BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Carlos Shahbazi Alonso (University of Hamburg\, Dept. of Mathemati
cs)
DTSTART:20201223T150000Z
DTEND:20201223T163000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/1
DESCRIPTION:Title: Parallel spinors on globally hyperbolic Lorentzian four-manif
olds\nby Carlos Shahbazi Alonso (University of Hamburg\, Dept. of Math
ematics) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract
\nI will discuss the differential geometry and topology of globally hyperb
olic four-manifolds (M\,g) admitting a parallel real spinor ε. Using the
theory of parabolic pairs recently introduced in\narXiv:1911.08658 \, I wi
ll first formulate the parallelicity condition of ε on M as a system of p
artial differential equations\, the parallel spinor flow equations\, for a
family of polyforms on any given Cauchy surface Σ↪M. Existence of a pa
rallel spinor on (M\,g) induces a system of constraint\npartial differenti
al equations on Σ\, which we prove to be equivalent to an exterior differ
ential system involving a cohomological condition on the shape operator of
the embedding Σ↪M. Solutions of this differential system are precisely
the allowed initial data for the evolution problem of a\nparallel spinor
and define the notion of parallel Cauchy pair (e\,Θ)\, where e is a cofra
me and Θ is a symmetric two-tensor. I will characterize all parallel Cauc
hy pairs on simply connected Cauchy surfaces\, refining a result of Baum\,
Leistner\, and Lischewski. Furthermore\, I will classify all\ncompact thr
ee-manifolds admitting parallel Cauchy pairs\, proving that they are canon
ically equipped with a locally free action of R2 and are isomorphic to cer
tain torus bundles over S1. Moreover\, I will classify all left-invariant
parallel Cauchy pairs on simply connected Lie groups\, specifying when the
y are allowed initial data for the Ricci flat equations and when the shape
operator is Codazzi. Finally\, I will give a novel geometric interpretati
on of a class of parallel spinor flows and solve it in several examples\,
obtaining explicit families of four-dimensional Lorentzian manifolds carry
ing parallel spinors."\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics)
DTSTART:20201125T150000Z
DTEND:20201125T163000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/2
DESCRIPTION:Title: The duality-covariant formulation of Abelian gauge theories o
n Riemannian four-manifolds\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of
Theoretical Physics) as part of Geometry and Physics @ NIPNE\, Bucharest\
n\n\nAbstract\nI describe the manifestly duality-covariant formulation of
Abelian gauge theories on Riemannian four-manifolds. This relies on the no
tion of parataming of a symplectic vector bundle\, a paracomplex analogue
of the classical notion of symplectic taming which appropriately encodes a
ll gauge couplings and theta angles (the so-called "gauge kinetic function
s") of the theory when working in Euclidean signature. In this formulation
\, the solutions of the theory are polarized anti-selfdual connections on
a principal bundle with split weakly Abelian structure group\, which give
a manifestly duality-covariant description of Euclidean dyons\, including
far-reaching generalizations of ordinary dyons called\ndyonic U-folds.\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics)
DTSTART:20201021T140000Z
DTEND:20201021T153000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/3
DESCRIPTION:Title: The classification of principal bundles with weakly Abelian s
tructure group\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical
Physics) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract
\nI briefly describe the geometry and topological classification of princi
pal bundles whose structure group is a Lie group with Abelian Lie algebra.
Such groups are generally disconnected and non-Abelian\, but their connec
ted component of the identity is an Abelian Lie group. Such principal bund
les appear in certain physical theories\, such as in "Abelian" gauge theor
ies in 4 dimensions with electro-magnetic duality.\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics)
DTSTART:20201028T150000Z
DTEND:20201028T163000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/4
DESCRIPTION:Title: Connections on principal bundles with weakly Abelian structu
re group\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physic
s) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI gi
ve a brief account of the theory of principal and adjoint connections on p
rincipal bundles with weakly Abelian structure group and describe the univ
ersal Chern-Weil morphism of such groups. Such\nconnections model gauge po
tentials in certain physical gauge theories\, such as "Abelian" gauge theo
ries with manifest electromagnetic duality.\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics)
DTSTART:20201104T150000Z
DTEND:20201104T163000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/5
DESCRIPTION:Title: The duality-covariant formulation of classical Abelian gauge
theories\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physic
s) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI gi
ve a brief account of the duality-covariant formulation of classical Abeli
an gauge theories of rank n defined on a Lorenzian 4-manifold (of which or
dinary electromagnetism is a very special example when n=1). At the level
of field strengths\, such theories admit a formulation as twisted self-dua
l theories\, which is manifestly covariant with respect to electro-magneti
c duality. Imposing the appropriate version of the Dirac integrality condi
tion leads to a description of such theories\nin terms of gauge potentials
described by connections on a principal bundle with weakly Abelian struct
ure group G\, which in the case at hand is the group of affine transformat
ions of a special symplectic torus. Namely\, G is a semidirect product of
a 2n-dimensional torus group A with a\ndiscrete group \\Gamma which is a m
odified Siegel modular group.\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlos Shahbazi Alonso (Univ. of Hamburg\, Dept. of Mathematics)
DTSTART:20210120T150000Z
DTEND:20210120T163000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/6
DESCRIPTION:Title: Heterotic solitons on four-manifolds\nby Carlos Shahbazi
Alonso (Univ. of Hamburg\, Dept. of Mathematics) as part of Geometry and P
hysics @ NIPNE\, Bucharest\n\n\nAbstract\nI will discuss four-dimensional
Heterotic solitons\, defined as a particular class of solutions of the equ
ations of motion of Heterotic supergravity on a four-manifold $M$. Heterot
ic solitons depend on a parameter $\\kappa$ and consist of a Riemannian me
tric $g$\, a metric connection with skew torsion $H$ on $TM$ and a closed
one-form $\\varphi$ on $M$. In the limit $\\kappa \\to 0$\, Heterotic soli
tons reduce to a class of generalized Ricci solitons and can be considered
as a higher-order curvature modification of the latter. If the torsion $H
$ is identified with the Hodge dual of $\\varphi$\, Heterotic solitons con
sist of either flat tori or closed Einstein-Weyl structures on manifolds o
f type $S^1\\times S^3$ as introduced by P. Gauduchon. More generally\, I
will construct several families of Heterotic solitons as suspensions of ce
rtain three-manifolds with prescribed constant principal Ricci curvatures\
, amongst which we find hyperbolic manifolds\, manifolds covered by $\\mat
hrm{Sl}(2\,\\mathbb{R})$ and E$(1\,1)$ or certain Sasakian three-manifolds
. These solutions exhibit a topology dependence in the string slope parame
ter $\\kappa$ and yield\, to the best of our knowledge\, the first example
s of Heterotic compactification backgrounds not locally isomorphic to supe
rsymmetric compactification backgrounds. Work in collaboration with Á. Mu
rcia and A. Moroianu.\n\nThis is a joint seminar "Geometry & Physics @ NIP
NE" and "Geometry @ IMAR"\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gaetan Borot (Humboldt University of Berlin)
DTSTART:20210127T150000Z
DTEND:20210127T163000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/7
DESCRIPTION:Title: Double Hurwitz numbers\, topological recursion and ELSV-type
formulas\nby Gaetan Borot (Humboldt University of Berlin) as part of G
eometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nHurwitz theory is c
oncerned with the enumeration of branched coverings of P^1 with given topo
logy and constrained ramification. It can be approached/solved in at least
three ways: integrable hierarchies coming from the representation theory
of the symmetric (first unveiled by Okounkov and Pandharipande)\, intersec
tion theory on the moduli space of curves (first seen in the Ekedahl-Lando
-Shapiro-Vainshtein formula)\, and topological recursion (taking its roots
in Bouchard-Marino conjecture). These three aspects have been established
for many different type of Hurwitz problems\, and after a brief review I
will focus on double Hurwitz numbers where the three structures enrich eac
h other: a joint work with Do\, Karev\, Lewanski and Moskowsky\, we start
from known representation-theoretic formulas for double Hurwitz numbers to
prove a polynomiality result and topological recursion\, which in turn im
plies an ELSV-like formula involving Chiodo classes and generalising a for
mula of Johnson-Pandharipande-Tseng\, and proves along the way new vanishi
ng properties of the Chiodo class.\n\nThis is a joint seminar "Geometry &
Physics @ NIPNE" and "Geometry @ IMAR".\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Patrick Popescu-Pampu (Lille University)
DTSTART:20210209T080000Z
DTEND:20210209T093000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/8
DESCRIPTION:Title: The Combinatorics of Plane Curve Singularities\nby Patric
k Popescu-Pampu (Lille University) as part of Geometry and Physics @ NIPNE
\, Bucharest\n\n\nAbstract\nEver since Newton introduced the first combina
torial object in the study of singularities of plane curves\, later called
the "Newton polygon"\, several trees -- i.e. connected graphs without cyc
les -- were introduced in order to completely encode the combinatorial str
ucture of such a singularity. I will explain how\, starting from some Newt
on polygons associated to a deeper and deeper "microscopic"\nstudy of the
initial singularity\, one can construct a special simplicial bidimensional
complex -- a lotus -- in which all these trees embed. One can thus visual
ize the relations between all of them simultaneously\, in contrast with th
e previous situation\, in which there existed only algorithms relating two
such trees. My talk will consist of an introduction to the first chapter
of "Handbook of\nGeometry and Topology of Singularities I"\, recently writ
ten in collaboration with Evelia Garcia Barroso and Pedro Gonzalez Perez.\
n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "Geometry @ IM
AR".\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrien Boulanger (Univ. of Pisa)
DTSTART:20210216T080000Z
DTEND:20210216T093000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/9
DESCRIPTION:Title: A Cheeger like inequality for 1-forms\nby Adrien Boulange
r (Univ. of Pisa) as part of Geometry and Physics @ NIPNE\, Bucharest\n\nA
bstract: TBA\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "
Geometry @ IMAR".\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlos Shahbazi Alonso (Univ. of Hamburg)
DTSTART:20210324T150000Z
DTEND:20210324T160000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/10
DESCRIPTION:Title: Mathematical Supergravity and its applications to differenti
al geometry\nby Carlos Shahbazi Alonso (Univ. of Hamburg) as part of G
eometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI will discuss the
recent developments in the mathematical theory of supergravity that lay th
e mathematical foundations of the universal bosonic sector of four-dimensi
onal ungauged supergravity and its Killing spinor equations in a different
ial-geometric framework. I will provide the necessary context and backgro
und. explaining the results pedagogically from scratch and highlighting se
veral open mathematical problems which arise in the mathematical theory of
supergravity\, as well as some of its potential mathematical applications
. Work in collaboration with Vicente Cortés and Calin Lazaroiu.\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sergiu Moroianu (IMAR\, Bucharest)
DTSTART:20210316T080000Z
DTEND:20210316T093000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/11
DESCRIPTION:Title: The Gauss-Bonnet formula on polyhedra\nby Sergiu Moroian
u (IMAR\, Bucharest) as part of Geometry and Physics @ NIPNE\, Bucharest\n
\nAbstract: TBA\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" an
d "Geometry @ IMAR"\n\nMeeting ID: 932 0776 6496\nPasscode: 900082\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Calin Lazaroiu (NIPNE\, Bucharest)
DTSTART:20210406T070000Z
DTEND:20210406T083000Z
DTSTAMP:20260404T110914Z
UID:GAP-Bucharest/12
DESCRIPTION:Title: Spinor squares\, G-structures and Fierz potentials\nby C
alin Lazaroiu (NIPNE\, Bucharest) as part of Geometry and Physics @ NIPNE\
, Bucharest\n\n\nAbstract\nI give a brief summary of the spinor squaring a
pproach to studying solutions of generalized Killing spinor equations and
of some of its applications to the study of certain G-structures. I also d
iscuss\npotential functions which can be used to describe such G-structure
s as well as certain stratified versions thereof.\n\nMeeting ID: 998 2511
0103\n Passcode: 625488\n
LOCATION:https://stable.researchseminars.org/talk/GAP-Bucharest/12/
END:VEVENT
END:VCALENDAR