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BEGIN:VEVENT
SUMMARY:Dimitris Kosmopoulos (Univ. of Geneva)
DTSTART:20231031T100000Z
DTEND:20231031T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/1
DESCRIPTION:Title: Μελετώντας Βαρυτικά Κύματα με Πλάτη
Σκέδασης/Gravitational Waves from Amplitudes\nby Dimitris Kos
mopoulos (Univ. of Geneva) as part of NKUA HEP Seminars\n\nLecture held in
Αίθουσα σεμιναρίων του Τομέα (3ος όροφος
).\n\nAbstract\nΗ χρήση τεχνικών της Κβαντικής
Θεωρίας Πεδίου\, συγκεκριμένα η σύγχρονη
εργαλειοθήκη των Πλατών Σκέδασης\, για τ
ην ανάλυση βαρυτικών κυμάτων που παράγο
νται από δυαδικά συστήματα έχει οδηγήσε
ι σε ραγδαία πρόοδο τα τελευταία χρόνια.
Σε αυτή την ομιλία θα περιγράψω αυτή την
ερευνητική προσπάθεια\, δίνοντας ιδιαίτ
ερη έμφαση σε φαινόμενα συσχετισμένα με
το σπιν των αστροφυσικών σωμάτων που δημ
ιουργούν τα βαρυτικά κύματα\, καθώς και σ
τα πρώτα βήματα προς την περιγραφή δυαδι
κών συστημάτων με μεγάλη διαφορά στη μάζ
α (extreme-mass-ratio inspirals) χρησιμοποιώντας Πλάτ
η Σκέδασης.\n\nRecent years have seen significant advancements in
employing tools from Quantum Field Theory\, specifically Scattering Ampli
tudes\, to inform theoretical predictions for gravitational waveforms gene
rated by binary systems. In this talk I will review this effort\, emphasiz
ing especially results related to the spin of the astrophysical objects in
the binary system\, as well as the first steps towards a Quantum Field Th
eoretic description of extreme-mass-ratio inspirals.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthew Dodelson (CERN)
DTSTART:20231211T100000Z
DTEND:20231211T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/2
DESCRIPTION:Title: Black hole bulk-cone singularities\nby Matthew Dodelson (CERN)
as part of NKUA HEP Seminars\n\n\nAbstract\nCorrelators in field theories
at finite temperature have singularities on the light cone. Are there any
other singularities? In this talk I will address this question in the con
text of holographic theories in the black hole phase. Two points on the Ad
S boundary can be connected by a null geodesic in the bulk\, leading to a
so-called bulk-cone singularity. These new singularities were previously c
onjectured by analyzing the geodesic approximation\, but we will derive th
em in full generality by developing the technology of thermal Regge theory
. The functional form of the singularity leads to sharp signatures of the
AdS photon sphere in the boundary CFT\, including an identification of the
boundary dual of the angular velocity and Lyapunov exponent associated to
the photon sphere. I will also comment on the resolution of the singulari
ty by stringy effects.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sašo Grozdanov (Univ. of Edinburgh)
DTSTART:20231204T100000Z
DTEND:20231204T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/3
DESCRIPTION:Title: Pole-skipping in a large number of spacetime dimensions and the re
construction of QFT spectra\nby Sašo Grozdanov (Univ. of Edinburgh) a
s part of NKUA HEP Seminars\n\n\nAbstract\nThe holographic duality provide
s an explicit reduction of quantum field theory (QFT) calculations in the
semiclassical large-N limit to sets of “gravitational” differential eq
uations whose analysis can reveal all details of the spectra of thermal QF
T correlators. I will discuss how\, in certain cases\, a complete reconstr
uction of the spectrum and of the corresponding correlator is possible fro
m only the knowledge of an infinite\, discrete set of pole-skipping points
(a “0/0” in the associated correlation function) traversed by a singl
e (hydrodynamic) mode. The main step that will enable a unique reconstruct
ion will be a series expansion of the problem in an inverse number of spac
etime dimensions\, expanded around infinity. Conceptually\, this reduces t
he computation of a QFT correlator spectrum to performing a set of purely
algebraic manipulations.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicolaos Toumbas (Cyprus U.)
DTSTART:20240429T090000Z
DTEND:20240429T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/4
DESCRIPTION:Title: A time dependent ER=EPR for closed FRW cosmologies\nby Nicolao
s Toumbas (Cyprus U.) as part of NKUA HEP Seminars\n\n\nAbstract\nIn this
talk\, I will discuss extensions of the static patch holographic proposal
for de Sitter space and entanglement entropy calculation prescriptions to
generic closed FRW cosmologies in arbitrary dimensions. For large classes
of bouncing and Big Bang/Big Crunch cosmologies\, the spacetime can be enc
oded on two holographic screens at the apparent horizons associated to obs
ervers at antipodal points of the spatial sphere. The leading contribution
s to the entanglement entropy between the screens arise from a minimal ext
remal trapped or anti-trapped sphere in the region between the apparent ho
rizons. The picture amounts to a time-dependent\, cosmological realization
of the ER=EPR conjecture. For the Big Crunch contracting cases\, the scre
ens disentangle with the geometrical bridge between them closing off when
the minimal extremal trapped sphere hits the Big Crunch singularity at a t
ime before the collapse of the Universe.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Achilleas Lazopoulos (ETH\, Zurich)
DTSTART:20240122T100000Z
DTEND:20240122T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/5
DESCRIPTION:Title: Ενεργός θεωρία πεδίου για το Καθιερ
ωμένο Μοντέλο/Developments in Standard Model Effective Field T
heory\nby Achilleas Lazopoulos (ETH\, Zurich) as part of NKUA HEP Semi
nars\n\nLecture held in TBA.\n\nAbstract\nΠερίληψη:\n\nΗ μη α
νακάλυψη\, μέχρι τώρα\, καινούριων σωματι
δίων στο LHC υποδηλώνει ότι\, αν υπάρχουν τ
έτοια σωματίδια στην TeV κλίμακα\, η επίδρ
ασή τους στις μετρήσεις στο LHC θα είναι μ
όνο έμμεση. Η Ενεργός Θεωρία Πεδίου για τ
ο Καθιερωμένο Μοντέλο (ΕΘΠΚΜ) είναι ένα π
ολύ δημοφιλές θεωρητικό εργαλείο για τη
ν παραμετροποίηση παρόμοιων επιδράσεων\
, και τη διαμεσολάβηση ανάμεσα στη θεωρί
α και τα πειραματικά δεδομένα. Σ’αυτό το
σεμινάριο θα περιγράψω σύντομα την ΕΘΠΚ
Μ και μερικές θεωρητικές προκλήσεις που
αντιμετωπίζουμε σε ένα και δύο loops\, στην
προσπάθειά μας να κάνουμε τη θεωρητική
περιγραφή ακριβέστερη. \n\n---\n\nAbstract:\n\nThe lac
k of direct discoveries at the LHC implies that if there is new physics at
the TeV scale\, its effects will only influence collider observables indi
rectly. The Standard model effective field theory (SMEFT) is a very popula
r theoretical tool to parametrise the effects of new physics models\, and
therefore mediate between theory and experimental data. I will briefly des
cribe the SMEFT and some recent theoretical challenges at one and two loop
s\, as we strive to make the theoretical description more precise.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Elias Kiritsis (Univ. of Crete)
DTSTART:20231109T090000Z
DTEND:20231109T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/6
DESCRIPTION:Title: Holographic cosmological reheating [Canceled]\nby Elias Kirits
is (Univ. of Crete) as part of NKUA HEP Seminars\n\nLecture held in Αίθ
ουσα συνεδριάσεων του Τμήματος Φυσικής
ΕΚΠΑ (2ος όροφος).\n\nAbstract\nAccording to the inflationary
theory of cosmology\, most elementary particles in the current universe we
re created during a period of reheating after inflation. We self-consiste
ntly couple the Einstein-inflaton equations to a strongly coupled quantum
field theory (QFT) which is holographic.\n\nWe solve for the cosmological
evolution and show that this leads to an inflating universe\, a fast rehea
ting phase and finally a universe dominated by the QFT in thermal equilibr
ium.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nana Geraldine Cabo Bizet (Univ. de Guanajuato)
DTSTART:20231120T100000Z
DTEND:20231120T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/8
DESCRIPTION:Title: Non-Abelian T-dualities in (0\,2) gauged linear sigma models\n
by Nana Geraldine Cabo Bizet (Univ. de Guanajuato) as part of NKUA HEP Sem
inars\n\n\nAbstract\nWe consider U(1) two dimensional gauged linear sigma
models with (0\,2) supersymmetry and global symmetries. We implement T-dua
lity by gauging the global symmetries and adding Lagrange multipliers\, vi
a the Roček-Verlinde procedure. First\, we find Abelian T-duals\, which m
atch the mirror symmetry case. Then\, we implement general non-Abelian T-
duality for models arising from a reduction of (2\,2) supersymmetry\; incl
uding instanton corrections. We study the case of CP1 target space with S
U(2) global symmetry\, obtaining as a dual space the disk. We determine th
e non-Abelian SU(2)xSU(2) dual of CP1xCP1\, which consists of two copies
of the disk. We fully solve the equations of motion leading to non-Abelian
T-duality\, improving with respect to the studies for (2\,2) supersymmetr
y.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dimitrios Katsinis (NKUA)
DTSTART:20240108T100000Z
DTEND:20240108T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/9
DESCRIPTION:Title: Generating solutions of sigma models efficiently\nby Dimitrios
Katsinis (NKUA) as part of NKUA HEP Seminars\n\nLecture held in Αίθο
υσα σεμιναρίων Τομέα Β.\n\nAbstract\nWe review the dres
sing method for the construction solutions of non linear sigma models give
n a known solutions. Specializing in the case of the O(N) model\, we show
that given a solution having appropriate free parameters\, it is possible
to apply the dressing method systematically (i.e. without solving any equa
tion) by taking advantage of the Pohlmeyer reduction and by rescaling the
free parameters. In this context the dressing method acts as a non linear
superposition rule\, merging a genuine solution of the sigma model with a
"virtual" one. Talk based on 2011.04610\, 2201.02493\, 2201.10554 and work
in progress.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlos Núñez (Swansea Uni.)
DTSTART:20240212T100000Z
DTEND:20240212T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/10
DESCRIPTION:Title: Aspects of gauge-strings duality\nby Carlos Núñez (Swansea
Uni.) as part of NKUA HEP Seminars\n\n\nAbstract\nI will start with a peda
gogical introduction of Duality (in Physics) and AdS/CFT as an application
of these ideas. After that and more technically\, I will discuss how one
can use some techniques developed by string theorists to study non perturb
ative aspects of Quantum Field Theories that undergo phenomena like confin
ement\, symmetry breaking\, screening\, etc. The examples discussed will b
e taken from the papers I published in the last year.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shai Chester (Imperial College London)
DTSTART:20240304T100000Z
DTEND:20240304T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/11
DESCRIPTION:Title: Bootstrapping N = 4 SYM for all N and coupling\nby Shai Chest
er (Imperial College London) as part of NKUA HEP Seminars\n\n\nAbstract\nW
e combine supersymmetric localization with the numerical conformal bootstr
ap to bound the scaling dimension and OPE coefficient of the lowest-dimens
ion operator in N = 4 SU( N) super-Yang-Mills theory for a wide range of N
and Yang-Mills couplings g. We find that our bounds are approximately sat
urated by weak coupling results at small g. Furthermore\, at large N our b
ounds interpolate between integrability results for the Konishi operator a
t small g and strong-coupling results\, including the first few stringy co
rrections\, for the lowest-dimension double-trace operator at large g. In
particular\, our scaling dimension bounds describe the level splitting bet
ween the single- and double-trace operators at intermediate coupling.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Congkao Wen (QMUL)
DTSTART:20240115T100000Z
DTEND:20240115T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/12
DESCRIPTION:Title: Exact integrated correlators in N=4 super Yang-Mills\nby Cong
kao Wen (QMUL) as part of NKUA HEP Seminars\n\n\nAbstract\nOver the past f
ew years\, it has been shown that\, when integrating out the spacetime dep
endence with a certain integration measure\, some four-point correlation f
unctions in four-dimensional maximally supersymmetric Yang-Mills theory (N
=4 SYM) can be computed exactly. These physical observables are often call
ed integrated correlators\, which are functions of (complexified) Yang-Mil
ls coupling\, and transform under the S-duality of N=4 SYM. In this talk\,
I will review some of the recent developments regarding the integrated co
rrelators.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthew Roberts (APCTP)
DTSTART:20240123T100000Z
DTEND:20240123T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/13
DESCRIPTION:Title: Monodromy Defects in QFT and Holography\nby Matthew Roberts (
APCTP) as part of NKUA HEP Seminars\n\nLecture held in TBA.\n\nAbstract\nW
ith an aim to further quantify non-pertubative defects in quantum field th
eory\, we study two-dimensional magnetic defects in four dimensional SUSY
quantum field theories which preserve a two-dimensional superconformal sym
metry along the defect. These can be thought of as an infrared limit of a
magnetic solenoid. On general grounds such magnetic defects support locali
zed chiral edge states\, and in our system we generically preserve a (0\,2
) supersymmetry. We compute various physical observables such induced curr
ents rotating around the solenoid\, as well as central charges of the defe
ct\, as a function of the monodromies. Time permitting\, we also comment o
n the analagous case of one dimensional defects in three dimensional QFTs.
\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Geoffrey Compère (Brussels U. and Intl. Solvay Inst.\, Brussels)
DTSTART:20240326T100000Z
DTEND:20240326T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/14
DESCRIPTION:Title: Memory effects in de Sitter and the Lambda-BMS group\nby Geof
frey Compère (Brussels U. and Intl. Solvay Inst.\, Brussels) as part of N
KUA HEP Seminars\n\n\nAbstract\nI will first review the features of the di
splacement memory effect in asymptotically flat spacetimes. I will contras
t the asymptotic structure of future infinity in de Sitter spacetime to th
e one of null infinity in asymptotically flat spacetimes and explain how a
generalization of the BMS group of asymptotic symmetries\, the Lambda-BMS
group\, arises in de Sitter. I will then explain how to solve for the lin
ear graviton field in de Sitter for a localized quadrupolar source and der
ive the de Sitter memory effect and its relationship to the Lambda-BMS gro
up. I will prove that the analysis invalidates the dS4/CFT3 conjecture.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mehrdad Mirbabayi (ICTP)
DTSTART:20240311T100000Z
DTEND:20240311T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/15
DESCRIPTION:Title: An Observer's Measure of De Sitter Entropy\nby Mehrdad Mirbab
ayi (ICTP) as part of NKUA HEP Seminars\n\n\nAbstract\nThe two-point corre
lation function of a massive field\, measured along an observer's worldlin
e in de Sitter (dS)\, decays exponentially in time. Meanwhile\, every dS o
bserver is surrounded by a horizon and the holographic interpretation of t
he horizon entropy S_dS suggests that the correlation function should stop
decaying\, and start behaving erratically at late times. We find evidence
for this expectation in Jackiw-Teitelboim gravity by finding a topologica
lly nontrivial saddle\, which is suppressed by exp(-S_dS)\, and which give
s a constant contribution to the norm squared of the correlator. This cons
tant might have the interpretation of the late-time average over all micro
scopic theories that have the same low-energy effective description. Based
on arxiv-2311.07724.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Erik Tonni (SISSA)
DTSTART:20240527T090000Z
DTEND:20240527T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/17
DESCRIPTION:Title: Aspects of Entanglement Hamiltonians\nby Erik Tonni (SISSA) a
s part of NKUA HEP Seminars\n\n\nAbstract\nThe reduced density matrix of a
spatial subsystem can be written as the exponential of the entanglement (
modular) Hamiltonian\, hence this operator contains a lot of information a
bout the entanglement of the corresponding spatial bipartition. For some p
articular models\, states and bipartitions\, this operator is local\, but
in general it is expected to be non-local. \nWe discuss some entanglement
Hamiltonians in two-dimensional conformal field theory and\, in the case o
f free fermions\, also how to obtain them from lattice calculations. The m
odular conjugation is closely related to the modular Hamiltonian. We discu
ss the geometric action of this operator in two-dimensional conformal fiel
d theory and its holographic gravitational counterpart in terms of geodesi
c bit threads.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michele Redi (INFN\, Florence)
DTSTART:20240408T090000Z
DTEND:20240408T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/18
DESCRIPTION:Title: The meso-inflationary axion scenario\nby Michele Redi (INFN\,
Florence) as part of NKUA HEP Seminars\n\n\nAbstract\nIn this talk I will
describe a new scenario for the QCD axion where the Peccei-Quinn symmetry
is broken after the beginning of visible inflation. This regime interpola
tes between popular pre-inflationary and post-inflationary axion scenarios
with different phenomenological features from both. In particular in some
region of parameters the PQ symmetry breaking is visible after QCD confin
ement\, modifying the axion dark matter abundance and with novel predictio
ns for axion mini-clusters. I will then show\, using the stochastic formal
ism of inflation\, that the meso-inflationary regime is realized even in t
he simplest scenario\, the KSVZ axion\, when the decay constant of the axi
on is comparable to the Hubble scale during inflation for specific values
of the quartic coupling.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Αντωνία Παρασκευoπούλου (Max Planck Inst. Mun
ich & LMU Munich)
DTSTART:20240513T090000Z
DTEND:20240513T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/19
DESCRIPTION:Title: Is M-theory emergent?\nby Αντωνία Παρασκευoπ
ούλου (Max Planck Inst. Munich & LMU Munich) as part of NKUA HEP Sem
inars\n\nLecture held in High Energy Group seminar room\, 3rd floor.\n\nAb
stract\nIn this talk\, I will present recent progress in the Swampland Pro
gram\, which I will briefly introduce\, focusing primarily on one of its l
ess established conjectures\, usually referred to as the Emergence Proposa
l. This postulates that the low energy effective action of a quantum gravi
ty theory may be obtained by integrating out light towers of states appear
ing in various asymptotic regions of the moduli space. In doing so\, I wil
l review certain subtleties regarding the species scale\, considered to be
the energy scale where the effective description of gravity breaks down a
nd will serve as the scale distinguishing perturbative from non-perturbati
ve degrees of freedom. I will then proceed to motivate why the Emergence P
roposal seems to be naturally realized in the (not yet completely understo
od) decompactification limit to M-theory by reviewing recent calculations
of higher derivative couplings and independent arguments. The talk will be
based on: 2309.11551\, 2404.01371\, 2404.05801.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Grumiller (TU Wien)
DTSTART:20240521T090000Z
DTEND:20240521T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/20
DESCRIPTION:Title: Carroll black holes\nby Daniel Grumiller (TU Wien) as part of
NKUA HEP Seminars\n\n\nAbstract\nAfter laying dormant for about half a ce
ntury\, Carroll symmetries recently attracted considerable attention\, in
part because conformal Carroll symmetries are equivalent to the BMS symmet
ries found in asymptotically flat spacetimes and thus play a key role in f
lat space holography. Making Carroll symmetries local yields Carroll gravi
ty\, which I shall review. We define Carroll black holes as solutions of C
arroll gravity that exhibit Carroll thermal properties and have a Carroll
extremal surface\, notions explained in my talk. [arXiv:2308.10947]\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Γεώργιος Λιναρδόπουλος (Asia-Pacific Center f
or Theoretical Physics)
DTSTART:20240520T090000Z
DTEND:20240520T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/21
DESCRIPTION:Title: B-type anomaly coefficients of holographic defects\nby Γεώ
ργιος Λιναρδόπουλος (Asia-Pacific Center for Theoretical
Physics) as part of NKUA HEP Seminars\n\nLecture held in High Energy Grou
p seminar room\, 3rd floor.\n\nAbstract\nEven dimensional conformal field
theories (CFTs) develop conformal/Weyl anomalies which inflict a (non-vani
shing) expectation value on the trace of the energy-momentum/stress tensor
. The presence of boundaries in CFTs gives rise to extra anomaly coefficie
nts and extra central charges\, which show up in both even and odd dimensi
ons and can be used to classify defect CFTs\, much like central charges ar
e used to classify pure CFTs.\n\nThis talk is about the computation of bou
ndary anomaly coefficients in (codimension-1) holographic defect CFTs. The
se are described by domain wall versions of N = 4 SYM that are holographic
ally dual to the D3-D5 and the D3-D7 probe-brane systems. Starting from th
e explicit expression of the improved energy-momentum tensor of N = 4 SYM\
, we will determine its two and three-point functions in the presence of t
he domain walls and extract the boundary anomaly coefficients\, to leading
order in perturbation theory. In the same process\, we will also determin
e the two and three-point function of the corresponding displacement opera
tors.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Georgios Palkanoglou (University of Guelp and TRIUMF)
DTSTART:20240708T090000Z
DTEND:20240708T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/22
DESCRIPTION:Title: Εξωτική πυρηνική υπερρευστότητα σε
πυρήνες και πυρηνική ύλη\nby Georgios Palkanoglo
u (University of Guelp and TRIUMF) as part of NKUA HEP Seminars\n\n\nAbstr
act\nΤα πυρηνικά υπερρευστά δημιουργούντα
ι απο την συμπύκνωση ζευγών νουκλεονίων\
, και η υπαρξή τους τόσο στους πυρήνες όσ
ο και στην εκτεταμένη πυρηνική ύλη\, έχει
πλέον εδραιωθεί\, φέροντας ποιοτικά απο
τελέσματα στο φάσμα και τις μάζες πυρηνώ
ν καθώς και στις θερμικές και περιστροφι
κές ιδιότητες των αστέρων νετρονίων. Ωστ
όσo\, η ακριβής τους δομή παραμένει ένα ση
μαντικό πρόβλημα της πυρηνικής θεωρίας.
Σε αυτή την ομιλία\, ξεκινώντας με την πυ
ρηνική ύλη\, θα παρουσιάσω ακριβείς ab initio
υπολογισμούς μικροσκοπικών ιδιοτήτων υ
πέρρευστης νετρονικής ύλης\, όπως η κατα
στατική της εξίσωση και η ενέργεια ζεύξη
ς των ζευγών που την αποτελούν\, σε όλο το
εύρως πυκνοτήτων του εξωτερικού φλοιού
του αστέρα νετρονίων. Αυτοί οι υπολογισμ
οί έχουν παραχθεί με τεχνικές Quantum Monte Carlo
και θα παρουσιάσω πως πρόμοιες τεχνικές
αυτή τη στιγμή εφαρμόζονται στην μελέτη
των υπερρευστών που αναμένονται σε μεγα
λύτερα βάθη στον αστέρα\, καθώς και την π
ιθανότητα ύπαρξης εξωτικών πυρηνικών υπ
ερρευστών (π.χ.\, καταστάσεις που σπάνε pari
ty και time-reversal συμμετρίες). Συνεχίζοντας σ
τους πεπρασμένους πυρήνες\, θα παρουσιάσ
ω αποτελέσματα που υποστηρίζουν την ύπα
ρξη εξωτικής υπερρευστότητας (απο ζεύγη
spin-triplet ή mixed-spin) και θα συζητήσω τις πειρα
ματικές προσπάθειες επιβεβαίωσης τους σ
ε μετρήσεις μάζας και φάσματος βαρέων πυ
ρήνων. Τέλος\, θα συζητήσω τις επιπτώσεις
όλων αυτών των υπολογισμών στη φυσική τ
ων cold atoms και πως αυτά μπορούν να οδηγήσο
υν ή/και να συμπληρώσουν την εικόνα μας γ
ια τη δομή και τις μορφές της υπέρρευστη
ς πυρηνικής ύλης.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dimitrios Tsimpis (IP2I\, Lyon)
DTSTART:20241029T100000Z
DTEND:20241029T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/23
DESCRIPTION:Title: Τhe importance of being open\nby Dimitrios Tsimpis (IP2I\, L
yon) as part of NKUA HEP Seminars\n\n\nAbstract\nI will talk about some in
teresting features of open cosmologies (i.e. four-dimensional spacetimes o
f Friedmann-Lemaître-Robertson-Walker type with three-dimensional spatial
slices that are hyperbolic) related to compactifications of ten-dimension
al supergravity on certain classes of six-dimensional spaces. Based on e-P
rints: $\\href{https://arxiv.org/abs/2210.10813}{2210.10813}$\, $\\href{ht
tps://arxiv.org/abs/2309.03938}{2309.03938}$ and $\\href{https://arxiv.org
/abs/2405.09323}{2405.09323}$.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jorge Russo (ICREA\, Barcelona and Barcelona\, Autonoma U. and ICC
\, Barcelona U.)
DTSTART:20241111T100000Z
DTEND:20241111T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/24
DESCRIPTION:Title: On the new formulation of self-dual nonlinear electrodynamics
\nby Jorge Russo (ICREA\, Barcelona and Barcelona\, Autonoma U. and ICC\,
Barcelona U.) as part of NKUA HEP Seminars\n\n\nAbstract\nAn important cla
ss of theories of nonlinear electrodynamics (NLED) are the self-dual ones\
,\nthat is\, theories invariant under electromagnetic duality. A well-know
n example is Born-Infeld theory. Until recently\, only a few other example
s were known. A new formulation leads to the explicit construction of the
most general self-dual nonlinear electrodynamics and leads to the complete
solution of the causality constraints. In addition\, the construction exh
ibits in a simple way the connection between causality and energy conditio
ns. A corollary is that there are no regular black holes in any causal NLE
D with zero cosmological constant.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eduardo Peinado (Universidad Nacional Autónoma de México (UNAM))
DTSTART:20240905T090000Z
DTEND:20240905T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/25
DESCRIPTION:Title: Recent results in phenomenology of light gauge bosons and dark ma
tter\nby Eduardo Peinado (Universidad Nacional Autónoma de México (U
NAM)) as part of NKUA HEP Seminars\n\nLecture held in Nuclear and Particle
Physics Division\, Seminar Room\, 3rd floor.\n\nAbstract\nThe Standard Mo
del has been confirmed with high precision across a wide range of energies
in numerous experiments. The LHC has significantly constrained new physic
s\, pushing potential discoveries to energy scales above the TeV range. De
spite this\, a light gauge boson remains a compelling extension to the Sta
ndard Model\, mainly due to its testability in upcoming low-energy experim
ents. In this talk\, we will review the potential effects of light gauge b
osons in current and future low-energy experiments\, such as CEvNS\, parit
y-violating electron scattering\, and electron-positron annihilation. Furt
hermore\, dark matter direct detection experiments provide complementary s
earch strategies if the new gauge boson mediates between the dark and visi
ble sectors.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robert Harris (Fermilab)
DTSTART:20241001T090000Z
DTEND:20241001T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/26
DESCRIPTION:Title: Searches for Single and Pair-Produced Dijet Resonances at CMS
\nby Robert Harris (Fermilab) as part of NKUA HEP Seminars\n\nLecture held
in Nuclear and Particle Physics Division\, Seminar Room\, 3rd floor.\n\nA
bstract\nSearches for resolved dijet resonances at CMS explore physics at
high mass\, and have\nplaced significant constraints on models of dark mat
ter\, grand unification\, quark\ncompositeness\, dynamical symmetry breaki
ng\, additional strong interactions\, new gauge\nbosons and extra dimensio
ns. Conducted for over three decades at hadron colliders\,\nthese searches
for s-channel production of a single dijet resonance (p p $\\to$ X $\\to$
jet jet)\,\nuse the simplest and highest mass signature of new physics wi
th jets. The next simplest\nsearch is pair production of resolved dijet re
sonances with identical masses\, produced\neither non-resonantly (p p $\\t
o$ X X $\\to$ [j j] [j j])\, or resonantly through a massive\nintermediate
state Y that itself decays to dijet resonances (p p $\\to$ Y $\\to$ X X $
\\to$ [j j] [j j]). During Run 2 of the LHC\, such a search for resonant p
air production of dijet resonances\nhas found hints of a possible new reso
nance at a mass of around 8 TeV\, which should be\neither confirmed or exc
luded by the data now accumulating during Run 3. Finally\, a new\nsearch i
s just beginning for resonant production of pairs of dijet resonances with
non-\nidentical masses (p p $\\to$ Y $\\to$ X Z $\\to$ [j j] [j j]). All
the above searches will also be pursued with jets tagged as bottom quarks.
I will discuss these searches\, that constitute a\ncontinuing program of
exploration of resolved dijet resonances\, pursued at CMS by a\nstrong col
laboration among Athens\, Fermilab\, and other institutions. At the LHC no
w\, and\nat the HL-LHC for the next generation\, these searches will conti
nue to probe the highest\navailable mass scales for new physics in jet fin
al states\, scales that will not be surpassed\nunless and until a higher e
nergy hadron collider is eventually built.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Avik Banerjee (University of Crete)
DTSTART:20240916T090000Z
DTEND:20240916T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/27
DESCRIPTION:Title: Nambu-Goto equations from 3D gravity\nby Avik Banerjee (Unive
rsity of Crete) as part of NKUA HEP Seminars\n\nLecture held in Nuclear an
d Particle Physics Division seminar room\, 3rd floor.\n\nAbstract\nIn this
talk\, I will demonstrate that the solutions of three-dimensional gravity
obtained by gluing two copies of a spacetime across a junction constitute
d of a tensile string are in one-to-one correspondence with the solutions
of the Nambu-Goto equation in the same spacetime up to a finite number of
rigid deformations. The non-linear Nambu-Goto equation satisfied by the av
erage of the embedding coordinates of the junction emerges directly from t
he junction conditions along with the rigid deformations and corrections d
ue to the tension. Therefore\, the equivalence principle generalizes non-t
rivially to the string. Our results are valid both in three-dimensional fl
at and AdS spacetimes. In the context of AdS$_3$/CFT$_2$ correspondence\,
our setup could be used to describe a class of interfaces in the conformal
field theory featuring relative time reparametrization at the interface w
hich encodes the solution of the Nambu-Goto equation corresponding to the
bulk junction.\n\nBased on 2404.02149 (accepted for publication in JHEP)\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthew Roberts (APCTP)
DTSTART:20241007T090000Z
DTEND:20241007T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/28
DESCRIPTION:Title: An update on holographic magnetic defects\nby Matthew Roberts
(APCTP) as part of NKUA HEP Seminars\n\n\nAbstract\nDefect CFTs provide a
n exciting new playground to study RG flows and their endpoints. After rev
iewing some basics of defect CFTs\, I will present a detailed study of sup
ersymmetric monodromy defects (also known as magnetic defects) in four and
three dimensional systems. We will measure the response of the system to
the insertion of the magnetic solenoid\, and in the four dimensional case
will calculate new central charges which appear in the trace anomaly. We c
lose by commenting on new possible monotonic quantities in these new mixed
dimensional systems.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Achilleas Porfyriadis (U. Crete)
DTSTART:20241001T110000Z
DTEND:20241001T120000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/29
DESCRIPTION:Title: Extreme Black Holes: Anabasis and Accidental Symmetry\nby Ach
illeas Porfyriadis (U. Crete) as part of NKUA HEP Seminars\n\n\nAbstract\n
The near-horizon region of black holes near extremality is universally AdS
2-like. In this talk I will first explain the SL(2) transformation propert
ies of the spherically symmetric linear perturbations of AdS2 x S2 and sho
w how their backreaction leads to the Reissner-Nordstrom black hole. This
backreaction with boundary condition change is called an anabasis. I will
then show that the linear Einstein equation near AdS2 x S2\, with or witho
ut additional matter\, enjoys an accidental symmetry that may be thought o
f as an on-shell large diffeomorphism of AdS2. These symmetries are able t
o map different physical solutions onto each other by acting as a lineariz
ed diffeomorphisms on perturbative solutions around AdS2.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eliezer Rabinovici (The Racah Institute of Physics)
DTSTART:20241126T100000Z
DTEND:20241126T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/30
DESCRIPTION:Title: Some Aspects of Complexity and Krylov Complexity\nby Eliezer
Rabinovici (The Racah Institute of Physics) as part of NKUA HEP Seminars\
n\n\nAbstract\nA review of the concept of Complexity as has emerged in stu
dying long time properties of systems including blackholes will be present
ed. Some emphasis will be made on describing features of a particular form
of Complexity\, the Krylov Complexity. These include its structure when
interpolating among various types of systems: free\, strongly integrable a
nd chaotic ones. Finally I will present a case where we have shown that th
e value of the Krylov Complexity\, a quantum information concept\, is equa
l to the value of a geodesic in a certain background\, a geometric concept
.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aristomenis Donos (Durham University)
DTSTART:20241217T100000Z
DTEND:20241217T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/31
DESCRIPTION:Title: Nearly critical superfluids and holography [CANCELED]\nby Ari
stomenis Donos (Durham University) as part of NKUA HEP Seminars\n\n\nAbstr
act\nI will discuss the low energy dynamics of finite temperature systems
which are close to a superfluid phase transition. In the regime\, the ampl
itude of the order parameter needs to be included in the description captu
red by the hydrodynamics of conserved quantities and the Goldstone mode. A
fter presenting a field theoretic construction of a suitable effective the
ory\, I will examine the phenomenology of suitable holographic systems.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chrysoula Markou (Pisa\, Scuola Normale Superiore)
DTSTART:20241209T100000Z
DTEND:20241209T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/33
DESCRIPTION:Title: On the deep string spectrum\nby Chrysoula Markou (Pisa\, Scuo
la Normale Superiore) as part of NKUA HEP Seminars\n\nLecture held in Semi
nar Room of Nuclear and Particle Physics Division.\n\nAbstract\nHow well d
o we understand string theory? As an indicator can be thought of the degre
e of our understanding of its spectrum. Yet\, other than comprising infini
tely many physical states of arbitrarily high spin and mass\, what does th
e string spectrum look like? Traditional methodologies can yield its state
content on a level-by-level basis\, a straightforward procedure which how
ever becomes cumbersome as the level increases. In this seminar\, we will
discuss a new\, covariant and efficient technology with which entire physi
cal trajectories can be excavated. It is based on the observation that the
Virasoro constraints in fact encode the generators of a bigger algebra\,
that is a symplectic algebra\, which commutes with the spacetime Lorentz a
lgebra. This enables constructing trajectories deeper inside the spectrum
as “clones” of simpler ones\, upon suitably dressing the latter\, depe
nding on the “depth” of the trajectory we aim to reach.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuela Kulaxizi (Trinity Coll.\, Dublin)
DTSTART:20250210T100000Z
DTEND:20250210T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/34
DESCRIPTION:Title: Comments on the bulk phase shift (eikonal phase)\nby Manuela
Kulaxizi (Trinity Coll.\, Dublin) as part of NKUA HEP Seminars\n\n\nAbstra
ct\nWe discuss the phase shift of a light particle moving in an AdS black
hole geometry in the context of holography. When the impact parameter is b
eyond a critical value\, the particle does not return to the boundary. We
discuss ways of interpreting this in the context of the dual CFT.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Markus B. Fröb (U. Leipzig)
DTSTART:20250310T100000Z
DTEND:20250310T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/35
DESCRIPTION:Title: Modular Hamiltonians\, relative entropy and the entropy-area law
in de Sitter spacetime\nby Markus B. Fröb (U. Leipzig) as part of NKU
A HEP Seminars\n\n\nAbstract\nIn a very general setting\, entropy quantifi
es the amount of information about a system that an observer has access to
. However\, in contrast to quantum mechanics\, in quantum field theory nai
ve measures of entropy are divergent. To obtain finite results\, one needs
to consider measures such as relative entropy\, which can be computed fro
m the modular Hamiltonian using Tomita--Takesaki theory.\n\nIn this talk\,
I will explain the connection between the quantum-mechanical expressions
for (relative) entropy\, the modular Hamiltonian and Tomita--Takesaki theo
ry. I then present two examples of modular Hamiltonians that were recently
derived: one for conformal fields in diamond regions of conformally flat
spacetimes (including de Sitter)\, and one for fermions of small mass in d
iamond regions of two-dimensional Minkowski spacetime. I will give results
for the relative entropy between the de Sitter vacuum state and a coheren
t excitation thereof in diamonds and wedges\, and show explicitly that the
result satisfies the expected properties for a relative entropy. Finally\
, I will use thermodynamic relations to determine the local temperature th
at is measured by an observer\, and consider the backreaction of the coher
ent excitation on the geometry to prove an entropy-area law for de Sitter
spacetime.\n\nBased on arXiv:2308.14797\, 2310.12185\, 2311.13990 and 2312
.04629.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Diego Trancanelli (Università di Modena)
DTSTART:20250513T090000Z
DTEND:20250513T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/36
DESCRIPTION:Title: Conformal defects and RG flows in ABJM\nby Diego Trancanelli
(Università di Modena) as part of NKUA HEP Seminars\n\n\nAbstract\nDefect
s play a central role in many contexts\, from condensed matter to quantum
gravity. The situations in which the bulk theory is conformal and the defe
ct inherits part of this symmetry -- the so-called defect conformal field
theories (dCFTs) -- have recently received a lot of attention\, also than
ks to new powerful methods to tackle them\, like supersymmetric localizati
on\, integrability or the bootstrap. A dCFT may be deformed by turning on
marginally relevant operators\, which trigger RG flows connecting differen
t fixed points. A natural arena where this phenomenon can be explored are
3-dimensional Chern-Simons theories coupled to matter. These are in fact k
nown to display a plethora of Wilson loops that can be used to define 1-di
mensional dCFTs living on their contours. In this talk we discuss a few ex
amples from an intricate web of RG flows connecting the dCFTs defined on t
he BPS and non-BPS Wilson loops of ABJM theory. We compute the anomalous d
imensions of the deforming operators\, establish g-theorems along the flow
s\, and also discuss the role played by cohomological anomalies and framin
g.\n\nBased on: 2211.16501\, 2305.01647\, 2312.13283\, 2410.10970\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andreas Mantziris (Universidade do Porto)
DTSTART:20250520T090000Z
DTEND:20250520T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/37
DESCRIPTION:Title: Gravitational waves from a curvature-induced phase transition of
a Higgs-portal dark matter sector\nby Andreas Mantziris (Universidade
do Porto) as part of NKUA HEP Seminars\n\n\nAbstract\nOur latest study (24
07.18845) investigates the possibility of generating gravitational waves (
GWs) from a curvature-induced phase transition of a non-minimally coupled
scalar field acting as dark matter\, with a portal interaction to the Higg
s field. This analysis is conducted within a dynamical spacetime framework
\, specifically during the transition from inflation to kination\, while a
lso examining the potential for triggering Electroweak symmetry breaking t
hrough this mechanism.\n\nA comprehensive exploration of inflationary scal
es is carried out\, considering both positive and negative values of the n
on-minimal coupling. The study further accounts for phenomenological and o
bservational constraints on the Beyond Standard Model (BSM) couplings\, en
suring consistency when the scalar field serves as spectator dark matter.
Notably\, kination enhances the GW amplitudes\, significantly restricting
the viable parameter space. While the resulting GW spectra typically resid
e at high frequencies for standard high-scale inflation\, certain regions
of parameter space allow for potential detection in future experiments\, o
ffering a testable link between early universe dynamics\, dark matter phys
ics\, and gravitational wave cosmology.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Georgios Tringas (Lehigh University)
DTSTART:20250610T090000Z
DTEND:20250610T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/38
DESCRIPTION:Title: Scale-separation from O-planes\nby Georgios Tringas (Lehigh U
niversity) as part of NKUA HEP Seminars\n\n\nAbstract\nOrientifold planes
play a crucial role in flux compactifications of string theory\, and we de
monstrate their deep connection to achieving scale-separated solutions. Sp
ecifically\, we show that when an orientifold plane contributes at leading
order to the non-zero value of the scalar potential\, then either the wea
k coupling limit or the large volume limit implies scale separation\, mean
ing that the Kaluza-Klein tower mass decouples from the inverse length sca
le of the lower-dimensional theory. Notably\, in the supergravity limit\,
such solutions are inherently scale-separated. This result is independent
of the spacetime dimension and the dimensionality of the Op-plane as long
as p < 7. Similarly\, we show that parametric scale separation is not poss
ible for isotropic compactifications with a leading curvature term that ge
nerically arise in the AdS/CFT context. We classify all possible flux comp
actification setups in both type IIA and type IIB string theory for Op-pla
nes with 2 ≤ p ≤ 6 and present their universal features. While the par
ametrically controlled scale-separated solutions are all AdS\, we also fin
d setups that allow for dS vacua. We prove that flux quantization prevents
these dS vacua from arising in a regime of parametric control.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dimitrios Tsimpis (IP2I\, Lyon)
DTSTART:20251027T100000Z
DTEND:20251027T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/39
DESCRIPTION:Title: Universal cosmologies\nby Dimitrios Tsimpis (IP2I\, Lyon) as
part of NKUA HEP Seminars\n\n\nAbstract\nUniversal cosmologies are exact s
olutions of 10d type IIA supergravity containing a 4d Friedmann-Lemaître-
Robertson-Walker factor\, that can also be repackaged as solutions of 4d m
odels\, i.e. as 4d consistent truncations. We extend the dynamical system
analysis of universal cosmologies\, beyond the case of a single exponentia
l potential. For an open universe (negative 3d spatial curvature)\, these
models generally possess many desirable features: parametric control of e-
folds\, late-time acceleration from potentials with steep exponentials (i.
e. in accordance with swampland bounds)\, small string-loop and α′-corr
ections\, scale separation and/or absence of decompactification.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aristomenis Donos (Durham University)
DTSTART:20250909T110000Z
DTEND:20250909T120000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/40
DESCRIPTION:Title: The Effective theory of Critical Superfluids\nby Aristomenis
Donos (Durham University) as part of NKUA HEP Seminars\n\n\nAbstract\nThe
dynamics of nearly critical superfluids have been extensively studied in t
he past\, in the context of statistical mechanics. I will discuss a covari
ant effective description which includes the hydrodynamics of the normal p
hase fluid at wavelengths comparable to the correlation length. I will obs
erve that the construction by Khalatnikov and Lebedev in 1978 was missing
a term important to find agreement with holographic calculations.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panagiotis Charalambous (SISSA\, Trieste and INFN\, Trieste)
DTSTART:20251007T090000Z
DTEND:20251007T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/41
DESCRIPTION:Title: Null infinity at the edge of a black hole\nby Panagiotis Char
alambous (SISSA\, Trieste and INFN\, Trieste) as part of NKUA HEP Seminars
\n\nLecture held in online.\n\nAbstract\nNull hypersurfaces are lightlike
surfaces that naturally emerge when asking questions like “what is an as
ymptotically flat spacetime?” or “what is a black hole?”. This gives
rise to the concepts of “null infinities” and “event horizons”. I
n this talk\, I will highlight the observation that all spacetimes that ar
e asymptotically flat near null infinity can be mapped through spatial inv
ersions onto the geometry near an extremal\, non-expanding and non-rotatin
g horizon located at a finite distance. This mapping is conformal\, ensuri
ng the dissimilar physics on each type of null surface\, but also emphasiz
ing their similarities. Typically\, the conformally related asymptotic geo
metries do not reside in the same spacetime. When they do\, however\, the
finite-distance horizon is a true black hole event horizon\, and the corre
sponding spatial inversions become conformal isometries of the spacetime t
hat exchange the two null surfaces. The prototypical example of this situa
tion is the four-dimensional extremal Reissner-Nordström black hole\, equ
ipped with the characteristic Couch-Torrence inversion conformal isometry.
This correspondence then enforces matching conditions between near-horizo
n and near–null-infinity data\, leading\, in particular\, to the identif
ication between infinite towers of conserved quantities: the near-horizon
Aretakis constants and the near–null-infinity Newman-Penrose constants.
I will also present hints of a broader relationship between disconnected n
ull hypersurfaces under less restrictive boundary conditions\, extending b
eyond extremal\, static horizons to include rotating or even non-extremal
cases.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marios Galanis (Stanford University)
DTSTART:20250930T090000Z
DTEND:20250930T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/42
DESCRIPTION:Title: Superradiant interactions of cosmic relics and how to look for th
em\nby Marios Galanis (Stanford University) as part of NKUA HEP Semina
rs\n\n\nAbstract\nIn this talk I will do three things. First\, I will outl
ine the conditions under which the interaction rate of inelastic processes
with a system consisting of N targets scales as N^2. Second\, I will pres
ent computations of interaction rates for several weakly interacting parti
cles\, including the cosmic neutrino background and axion dark matter\, an
d will explain the underlying physics. Third\, I will present a concrete e
xperimental protocol using Nuclear Magnetic Resonance that can extract the
se effects through quantum observables not relying on net energy transfer.
This protocol has the potential to significantly accelerate axion and dar
k photon dark matter searches and extend the reach of existing axion exper
iments to probe QCD axion-nuclear spin couplings. More broadly\, it paves
the way for detecting coherent inelastic interactions from other cosmic re
lics---most notably the cosmic neutrino background---and establishes nucle
ar-spin-based systems as a new class of quantum\, ultra-low-threshold dete
ctors.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giuseppe Bevilacqua (INPP Demokritos)
DTSTART:20251021T090000Z
DTEND:20251021T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/43
DESCRIPTION:Title: The Next To Next Challenge: towards numerical two-loop amplitude
reduction\nby Giuseppe Bevilacqua (INPP Demokritos) as part of NKUA HE
P Seminars\n\n\nAbstract\nThe Large Hadron Collider (LHC) started its firs
t beam in 2008. The data collected so far led to the discovery and charact
erisation of the Higgs boson and allowed important precision tests of the
Standard Model. In parallel to that\, continuous efforts are being made to
shed light on possible New Physics up to the energy frontier. Accurate sy
nergy between theory and experiment - and comparable precision on both sid
es - is key to foster discoveries. From the theory side\, the path to prec
ision runs through several directions. In several cases\, two-loop scatter
ing amplitudes are the bottleneck. In this talk I will discuss ongoing eff
orts towards integrand-level reduction of two-loop helicity amplitudes. Fi
rst I will describe a method for extracting the coefficients of the reduct
ion. I will elaborate on the advantages\, but also on the challenges\, of
performing numerical computations of two-loop integrands in the context of
dimensional regularisation. Finally I will discuss work underway to devel
op a numerical framework to achieve this goal.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Μαρία Γεροντίδου (NKUA)
DTSTART:20250915T103000Z
DTEND:20250915T120000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/44
DESCRIPTION:Title: Μετρητές Νετρονίων: Θεμελιώδης Έρε
υνα και Εφαρμογές\nby Μαρία Γεροντίδου (
NKUA) as part of NKUA HEP Seminars\n\n\nAbstract\nΠρόγραμμα σε
μιναρίων για την θέση Επίκουρου Καθηγητ
ή\nΠειραματικής Φυσικής Στοιχειωδών Σωμ
ατιδίων (APP35102)\nΤομέας Πυρηνικής Φυσικής
και Φυσικής Στοιχειωδών Σωματιδίων\, Τμή
μα Φυσικής\, ΕΚΠΑ\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Αντώνης Αγαπητός (Peking U.\, SKLNPT)
DTSTART:20250915T120000Z
DTEND:20250915T133000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/45
DESCRIPTION:Title: Advancing LHC physics with ML: Recent CMS results in boosted topo
logies\, jet tagging\, and beyond\nby Αντώνης Αγαπητός
(Peking U.\, SKLNPT) as part of NKUA HEP Seminars\n\n\nAbstract\nΠρόγ
ραμμα σεμιναρίων για την θέση Επίκουρου
Καθηγητή\nΠειραματικής Φυσικής Στοιχειω
δών Σωματιδίων (APP35102)\nΤομέας Πυρηνικής Φ
υσικής και Φυσικής Στοιχειωδών Σωματιδί
ων\, Τμήμα Φυσικής\, ΕΚΠΑ\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ευστάθιος Καρέντζος (Universität Bonn)
DTSTART:20250916T070000Z
DTEND:20250916T083000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/46
DESCRIPTION:Title: Ενοποιώντας Συστήματα\, Ανιχνευτές
και Ανάλυση με Μηχανική Μάθηση: Μια Ερευ
νητική Διαδρομή στο Μιονικό Φασματόμετρ
ο του πειράματος ATLAS\nby Ευστάθιος Καρέν
τζος (Universität Bonn) as part of NKUA HEP Seminars\n\n\nAbstract\n
Πρόγραμμα σεμιναρίων για την θέση Επίκο
υρου Καθηγητή\nΠειραματικής Φυσικής Στο
ιχειωδών Σωματιδίων (APP35102)\nΤομέας Πυρην
ικής Φυσικής και Φυσικής Στοιχειωδών Σω
ματιδίων\, Τμήμα Φυσικής\, ΕΚΠΑ\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Γεώργιος Κριντήρας (University of Kansas)
DTSTART:20250916T083000Z
DTEND:20250916T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/47
DESCRIPTION:Title: Το άλλο 95%: Αναζητώντας την προέλευσ
η της μάζας\nby Γεώργιος Κριντήρας (Universi
ty of Kansas) as part of NKUA HEP Seminars\n\n\nAbstract\nΠρόγραμμ
α σεμιναρίων για την θέση Επίκουρου Καθη
γητή\nΠειραματικής Φυσικής Στοιχειωδών
Σωματιδίων (APP35102)\nΤομέας Πυρηνικής Φυσι
κής και Φυσικής Στοιχειωδών Σωματιδίων\,
Τμήμα Φυσικής\, ΕΚΠΑ\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Στυλιανός Αγγελιδάκης (NKUA)
DTSTART:20250916T103000Z
DTEND:20250916T120000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/48
DESCRIPTION:Title: Ανακατασκευή & Συνδυασμένη Απόδοση
Μιονίων για το Πρόγραμμα Φυσικής του ATLAS<
/a>\nby Στυλιανός Αγγελιδάκης (NKUA) as part of NKUA H
EP Seminars\n\n\nAbstract\nΠρόγραμμα σεμιναρίων για
την θέση Επίκουρου Καθηγητή\nΠειραματικ
ής Φυσικής Στοιχειωδών Σωματιδίων (APP35102)
\nΤομέας Πυρηνικής Φυσικής και Φυσικής Σ
τοιχειωδών Σωματιδίων\, Τμήμα Φυσικής\, Ε
ΚΠΑ\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Δήμητρα Τσιώνου (National Taiwan University)
DTSTART:20250916T120000Z
DTEND:20250916T133000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/49
DESCRIPTION:Title: Μετρήσεις ακρίβειας με ανιχνευτές
στοιχειωδών σωματιδίων\nby Δήμητρα Τσι
ώνου (National Taiwan University) as part of NKUA HEP Seminars\n\n\nAb
stract\nΠρόγραμμα σεμιναρίων για την θέση Ε
πίκουρου Καθηγητή\nΠειραματικής Φυσικής
Στοιχειωδών Σωματιδίων (APP35102)\nΤομέας Πυ
ρηνικής Φυσικής και Φυσικής Στοιχειωδών
Σωματιδίων\, Τμήμα Φυσικής\, ΕΚΠΑ\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuela Kulaxizi (Trinity College Dublin and NKUA)
DTSTART:20251111T100000Z
DTEND:20251111T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/50
DESCRIPTION:Title: Photon trajectory beyond the critical impact parameter\nby Ma
nuela Kulaxizi (Trinity College Dublin and NKUA) as part of NKUA HEP Semin
ars\n\n\nAbstract\nWhen a highly energetic particle traverses a black hole
experiences a time delay and angular deflection\, which combine easily to
produce a standard phase shift for scattering off a very massive particle
. The picture drastically changes when the impact parameter attains values
beyond a critical one\; then the phase shift acquires a small imaginary p
art\, indicating inelastic scattering. What happens to the original time d
elay and deflection quantities?Do their complex valued counterparts for im
pact parameters beyond the photosphere make sense? We will investigate thi
s question in the context of an AdS black hole and the dual CFT descriptio
n.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Constantin Bachas (Ecole Nomermale Superiere & NTUA)
DTSTART:20251125T100000Z
DTEND:20251125T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/51
DESCRIPTION:Title: Holographic tension and the radiation-reaction problem\nby Co
nstantin Bachas (Ecole Nomermale Superiere & NTUA) as part of NKUA HEP Sem
inars\n\n\nAbstract\nI will explain how AdS/CFT allows to define two indep
endent notions of invariant brane tension in gravity. I will prove that su
persymmetry identifies them\, and explain the relevance of this observatio
n for the old radiation-reaction problem of accelerating charges and heavy
quarks.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Grégoire Olivier Mathys (EPFL)
DTSTART:20251209T100000Z
DTEND:20251209T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/52
DESCRIPTION:Title: Averaged null energy and the renormalisation group\nby Grégo
ire Olivier Mathys (EPFL) as part of NKUA HEP Seminars\n\n\nAbstract\nThe
averaged null energy operator (ANEC) is a light-ray integral of the null e
nergy\, which is known to have far-reaching consequences in CFT\, such as
the Lorentzian Inversion Formula. It is also closely connected to modular
Hamiltonian in QFT. In this talk\, I will discuss a new connection between
the ANEC operator and monotonicity of the renormalization group. In parti
cular\, I will show how the 2d c-theorem and 4d a-theorem can be derived u
sing the ANEC. This derivation relies on contact terms appearing in specif
ic ANEC correlators. I will also review a new infinite set of constraints
that can be derived from the ANEC in 2d QFT. This program hints at a more
general role for light-ray operators in QFT\, which I will argue for.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gonzalo Torroba (Centro Atomico Bariloche)
DTSTART:20260210T130000Z
DTEND:20260210T140000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/53
DESCRIPTION:Title: Quantum information\, entanglement\, and RG flows in AdS\nby
Gonzalo Torroba (Centro Atomico Bariloche) as part of NKUA HEP Seminars\n\
n\nAbstract\nQuantum information–theoretic ideas have recently provided
new insights into quantum field theory in curved space-times. In this talk
we present a nonperturbative inequality for the entanglement entropy of q
uantum field theory in rigid AdS space-time\, derived using tools from qua
ntum information theory. This result implies the irreversibility of renorm
alization group flows in AdS in 1+1\, 2+1 and 3+1 space-time dimensions. I
n the second part of the talk we discuss on-going work aimed at understand
ing the entanglement properties of free field theories in AdS\, including
analytic results in 1+1 dimensions and numerical analyses in 2+1 and 3+1 d
imensions.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Plefka (Humboldt U.\, Berlin)
DTSTART:20251202T100000Z
DTEND:20251202T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/54
DESCRIPTION:Title: High-precision gravitational wave physics from worldline quantum
field theory\nby Jan Plefka (Humboldt U.\, Berlin) as part of NKUA HEP
Seminars\n\n\nAbstract\nThe gravitational two-body problem has been funda
mental to physics since Newton's time. With the advent of gravitational wa
ve astronomy and the anticipated third generation of gravitational wave de
tectors in the 2030s\, there is an increasing need for high-precision pred
ictions from Einstein's theory of gravity regarding the encounters of blac
k holes and neutron stars in our universe.\nFascinatingly\, perturbative q
uantum field theory methods—developed for high-precision predictions of
elementary particle scattering at the LHC—have proven remarkably efficie
nt for this classical physics problem. This unexpected connection has led
to inspiring synergies between collider and gravitational wave physics.\n\
nIn my talk\, I will present our approach using a worldline quantum field
theory inspired by string theory\, which has emerged as the most efficient
tool for quantifying the scattering of spinning black holes. We have achi
eved highest-precision perturbative results for the scattering angle\, rad
iated energy\, and momentum recoil of such black hole encounters at the fi
fth order in Newton's gravitational coupling G\, assuming a mass hierarchy
between the two bodies. This four-loop calculation has moreover revealed
a new class of mathematical functions related to Calabi-Yau manifolds\, pr
eviously studied only in mathematics and string theory compactifications\,
here appearing for the first time in a physics context.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ioannis Tsiares (IPhT\, Saclay and LPENS\, Paris)
DTSTART:20260224T100000Z
DTEND:20260224T110000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/55
DESCRIPTION:Title: Analytic Conformal Bootstrap in two-dimensions and AdS$_3$ gravit
y\nby Ioannis Tsiares (IPhT\, Saclay and LPENS\, Paris) as part of NKU
A HEP Seminars\n\n\nAbstract\nΤα τοπικά δεδομένα (local da
ta) ισχυρά αλληλεπιδρώντων Σύμμορφων Θεω
ριών Πεδίου (CFTs) περιορίζονται αυστηρά --
και σε ορισμένες περιπτώσεις καθορίζοντ
αι πλήρως -- από βασικές συνθήκες όπως η μ
οναδιακότητα (unitarity) και η τοπικότητα (local
ity). Αυτό το πλαίσιο έχει γίνει γνωστό ως
το ``Conformal Bootstrap''. Σε δύο χωροχρονικές δια
στάσεις\, το bootstrap είναι κατά μία έννοια π
ιο ισχυρό λόγω της παρουσίας της άπειρης
διάστασης άλγεβρας Virasoro. Θα συζητήσουμε
πρόσφατα αποτελέσματα στο Virasoro analytic bootst
rap και τη σύνδεσή τους\, μέσω AdS/CFT\, με το π
ρόβλημα της τρισδιάστατης βαρύτητας σε A
dS. Πιο συγκεκριμένα\, θα παρουσιάσω πρόσφ
ατη πρόοδο προς την αναλυτική κατανόηση
των λεγόμενων Virasoro crossing kernels — απαραίτητ
α δομικά στοιχεία της crossing equation— και το
πώς αυτή η δομή συνδέεται με την κβαντικ
ή βαρύτητα στον AdS$_3$ μέσω της λεγόμενης ``
Virasoro TQFT''.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Masahide Yamaguchi (Institute for Basic Science (IBS) and Tokyo In
stitute of Technology (TIT))
DTSTART:20260615T090000Z
DTEND:20260615T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/56
DESCRIPTION:Title: Cosmological first-order phase transitions: tunneling at finite t
emperature\nby Masahide Yamaguchi (Institute for Basic Science (IBS) a
nd Tokyo Institute of Technology (TIT)) as part of NKUA HEP Seminars\n\n\n
Abstract\nCosmological phase transitions\, especially first order phase tr
ansitions\, have attracted renewed interest as potential sources of gravit
ational waves. Accurately predicting the resulting gravitational wave sign
al requires a reliable estimate of the transition rate\, which is governed
by a saddle-point configuration known as the bounce solution. The seminal
work of Coleman\, Glaser\, and Martin established that at zero temperatur
e\, any nontrivial bounce solution to the equations of motion that minimiz
es the Euclidean action is O(D)-symmetric in D-dimensional spacetime. At f
inite temperature\, however\, it has not been proven that an O(D-1)-symmet
ric bounce solution in the spatial directions indeed yields the minimal Eu
clidean action\, despite this assumption being widely used in the literatu
re. In this talk\, we extend the Coleman–Glaser–Martin analysis to fin
ite temperature. We rigorously prove that for a broad class of scalar pote
ntials\, any saddle-point configuration with the least action is necessari
ly O(D-1)-symmetric and monotonic in the spatial directions. This result p
rovides a firm mathematical foundation for the symmetry properties widely
assumed in studies of thermal vacuum decay and cosmological phase transiti
ons.\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dimitris Chatzis (Swansea University)
DTSTART:20260512T090000Z
DTEND:20260512T100000Z
DTSTAMP:20260404T100029Z
UID:NKUA-HEP/57
DESCRIPTION:by Dimitris Chatzis (Swansea University) as part of NKUA HEP S
eminars\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/NKUA-HEP/57/
END:VEVENT
END:VCALENDAR