BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:David Berenstein (UC Davis) DTSTART:20220516T010000Z DTEND:20220516T020000Z DTSTAMP:20260404T094752Z UID:NMTP2022/1 DESCRIPTION:Title: Aspects of the Quantum Mechanical Bootstrap\nby David Berenste in (UC Davis) as part of Numerical Methods in Theoretical Physics\n\n\nAbs tract\nI will detail some recent advances in understanding how to solve on e dimensional quantum mechanical problems with the numerical Bootstrap met hod for problems in the real line\, the circle and the positive real axis . Numerically\, convergence seems to be exponential in the real line and t he positive real axis problem. For the circle problem\, one obtains the ba nd structure of the potential. Finally\, I will describe some additional p rogress when dealing with Robin boundary conditions on the positive real axis problem.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Robert de Mello Koch (University of Witwatersrand) DTSTART:20220516T021500Z DTEND:20220516T031500Z DTSTAMP:20260404T094752Z UID:NMTP2022/2 DESCRIPTION:Title: Numerical Loop Space for Multi-matrix systems\nby Robert de Me llo Koch (University of Witwatersrand) as part of Numerical Methods in The oretical Physics\n\n\nAbstract\nWe revisit the problem of solving multi-ma trix quantum mechanics\, at large $N$\, numerically. The approach adopted uses collective field theory to give a loop space representation of the dy namics\, leading to a constrained optimization problem. The constraint is solved using a master-field parametrization. The complete fluctuation spec trum is also computable in the above scheme\, and is of immediate physical relevance. The numerical results presented prove that this approach solve s\, by numerical loop space methods\, the general two matrix model problem .\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Frank Pollmann (TUM) DTSTART:20220516T070000Z DTEND:20220516T080000Z DTSTAMP:20260404T094752Z UID:NMTP2022/3 DESCRIPTION:Title: Exploring Quantum Phases of Matter on Quantum Processors\nby F rank Pollmann (TUM) as part of Numerical Methods in Theoretical Physics\n\ n\nAbstract\nThe interplay of quantum fluctuations and interactions can yi eld novel quantum phases of matter with fascinating properties. Particular ly exciting physics is at play when confining systems to two spatial dimen sions. For this case it has been predicted that exotic quantum particles e merge —so-called “anyons”— that cannot exist in the three-dimensio nal world we live in. Understanding the physics of such system is a very c hallenging problem as it requires to solve quantum many body problems—wh ich is generically exponentially hard on classical computers.\n\nIn this c ontext\, universal quantum computers are potentially an ideal setting for simulating the emergent quantum many-body physics. In my talk\, I will dis cuss how to use existing (noisy) quantum computers to simulate quantum pha ses of matter. First\, I will consider symmetry protected topological pha ses (SPT) in one-dimensional systems. For this case\, ground states of Ham iltonians can be obtained using shallow quantum circuits and we can observ e a quantum phase transition between different SPT phases on a quantum dev ice. Second\, we prepare the ground state of the toric code Hamiltonian in two-dimensions using an efficient quantum circuit on a superconducting qu antum processor. We measure a topological entanglement entropy near the ex pected value of ln(2)\, and simulate anyon interferometry to extract the c haracteristic braiding statistics of the emergent excitations.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Masanori Hanada (University of Surrey) DTSTART:20220516T081500Z DTEND:20220516T091500Z DTSTAMP:20260404T094752Z UID:NMTP2022/4 DESCRIPTION:Title: Black Hole from Matrices\nby Masanori Hanada (University of Su rrey) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nM atrix models can describe black hole via holography. I will review numeric al approaches which were successful in the past\, and discuss the necessit y of new methods for tackling certain fascinating problems.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Pietro Brighi (IST Austria) DTSTART:20220517T010000Z DTEND:20220517T020000Z DTSTAMP:20260404T094752Z UID:NMTP2022/5 DESCRIPTION:Title: Tensor network approaches to the study of the interplay of large l ocalized systems and small thermal grains\nby Pietro Brighi (IST Austr ia) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nIn isolated quantum many-body systems\, thermalization is believed to occur d ue to the ergodicity of the system. While most physical systems indeed beh ave in an ergodic way and their dynamics leads to thermal equilibrium\, so me outstanding counterexamples exist. Many-body localization (MBL) provide s a paradigmatic case of ergodicity-breaking\, where strong disorder leads to the lack of relaxation to the thermal equilibrium.\n\nIn this talk I w ill present recent studies of the interplay of large non-interacting local ized chains and small ergodic baths. Using matrix product state (MPS) meth ods\, we probe the dynamics of these systems\, showing that in the strong interaction case not only the localized chain does not thermalize\, but it also leads to the localisation of the bath\, a phenomenon known as MBL pr oximity effect. The presence of the thermal inclusion\, however\, leads to a dramatic change in the system\, as it makes the localized particles int eract. As a consequence\, interesting entanglement patterns arise in the c hain\, a feature we dubbed propagation of MBL. Thanks to a phenomenologica l theory\, we are able to link the localisation of the thermal grain and t he phenomenon of propagation of MBL\, reproducing the characteristic entan glement behavior.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Kazuki Yamamoto (Kyoto University) DTSTART:20220517T021500Z DTEND:20220517T031500Z DTSTAMP:20260404T094752Z UID:NMTP2022/6 DESCRIPTION:Title: Finite-size scaling in a non-Hermitian XXZ spin chain\nby Kazu ki Yamamoto (Kyoto University) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nIn recent years\, open quantum systems have been a ctively studied both experimentally and theoretically\, as exemplified by driven-dissipative systems and non-Hermitian (NH) quantum systems. In this talk\, We demonstrate the universal properties of dissipative Tomonaga-Lu ttinger (TL) liquids by calculating correlation functions and performing f inite-size scaling analysis of a non-Hermitian XXZ spin chain as a prototy pical model in one-dimensional open quantum many-body systems [1]. Our ana lytic calculation is based on effective field theory with bosonization\, f inite-size scaling approach in conformal field theory\, and the Bethe-ansa tz solution. Our numerical analysis is based on the density-matrix renorma lization group generalized to non-Hermitian systems (NH-DMRG). We uncover that the model in the massless regime with weak dissipation belongs to the universality class characterized by the complex-valued TL parameter\, whi ch is related to the complex generalization of the c=1 conformal field the ory. As the dissipation strength increases\, the values of the TL paramete r obtained by the NH-DMRG begin to deviate from those obtained by the Beth e-ansatz analysis\, indicating that the model becomes massive for strong d issipation. Our results can be tested with the two-component Bose-Hubbard system of ultracold atoms subject to two-body loss.\n\n[1] Kazuki Yamamoto \, Masaya Nakagawa\, Masaki Tezuka\, Masahito Ueda\, and Norio Kawakami\, arXiv:2112.12467\, Phys. Rev. B in press.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Fabien Alet (CNRS) DTSTART:20220517T070000Z DTEND:20220517T080000Z DTSTAMP:20260404T094752Z UID:NMTP2022/7 DESCRIPTION:Title: Interior eigenvalue problem for localisable quantum lattice models in condensed matter\nby Fabien Alet (CNRS) as part of Numerical Metho ds in Theoretical Physics\n\n\nAbstract\nI will provide an overview of num erical techniques that have been proposed to obtain eigenstates deep in th e middle of the spectrum of many-body quantum systems. This problem is par ticularly relevant for systems which do not follow the eigenstate thermali zation hypothesis. I will discuss spectral transforms methods -- trying to review different strategies and works --\, and focus in particular ont the shift-invert technique. Examples of applications in the field of many- body localization will also be presented. In conclusion\, perspectives wil l be given on how to perhaps improve these methods and applications to oth er fields.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/7/ END:VEVENT BEGIN:VEVENT SUMMARY:David Luitz (University of Bonn) DTSTART:20220517T081500Z DTEND:20220517T091500Z DTSTAMP:20260404T094752Z UID:NMTP2022/8 DESCRIPTION:Title: Krylov space time evolution and quantum typicality\nby David L uitz (University of Bonn) as part of Numerical Methods in Theoretical Phys ics\n\n\nAbstract\nI will discuss how to perform exact time evolution of m any-body wave functions using Krylov space algorithms. This method only re lies on a fast matrix vector product of the Hamiltonian (or the evolution operator) and is the only method which can deal with similarly large syste ms in the regime of strong entanglement\, which is generically produced ov er time. In combination with the concept of quantum typically\, which allo ws us to get rid of traces over operators\, this method develops its full power.\nI will demonstrate this power with the example of how to calculate out of time order correlators in Heisenberg spin chains with short and lo ng range interactions.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Raghav Jha (Perimeter Institute) DTSTART:20220518T010000Z DTEND:20220518T020000Z DTSTAMP:20260404T094752Z UID:NMTP2022/9 DESCRIPTION:Title: New approach to continuous spin models in two and three dimensions \nby Raghav Jha (Perimeter Institute) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nWe apply tensor network methods to stud y the famous phase transition in the two-dimensional $O(2)$ model and a ge neralized version of this model that admits half-integer vortices in addi tion to the standard integer ones. We then consider the same model in thre e dimensions and carry out the first tensor study and locate the continuo us phase transition. Furthermore\, we introduce finite chemical potential and explore the Silver Blaze phenomenon by computing the particle number density. While the addition of chemical potential leads to a non-real acti on and is not suited for the standard Monte Carlo\, it is straightforward to study using tensors and presents itself as a strong contender over oth er numerical methods.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Anosh Joseph (IISER Mohali) DTSTART:20220518T021500Z DTEND:20220518T031500Z DTSTAMP:20260404T094752Z UID:NMTP2022/10 DESCRIPTION:Title: Complex Langevin Simulations of Dynamical Symmetry Breaking in IK KT Matrix Model\nby Anosh Joseph (IISER Mohali) as part of Numerical M ethods in Theoretical Physics\n\n\nAbstract\nIn this talk\, we report on t he results of complex Langevin simulations of the IKKT matrix model. This model is conjectured to be a nonperturbative formulation of superstring th eory in ten dimensions. Dynamical compactification of extra dimensions can be realized via spontaneous breaking of the model's SO(10) rotational sym metry. The phase of the Pfaffian in this model is inherently complex and t hus can make Monte Carlo simulations unreliable. The complex Langevin meth od can handle wild fluctuations in the phase of the Pfaffian and give reli able results. Our preliminary simulation results point to dynamical symmet ry breaking in the IKKT model.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Rak-Kyeong Seong (UNIST) DTSTART:20220518T070000Z DTEND:20220518T080000Z DTSTAMP:20260404T094752Z UID:NMTP2022/11 DESCRIPTION:Title: Machine Learning Calabi-Yau Volumes\nby Rak-Kyeong Seong (UNI ST) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nThe talk will give an overview of our work from 2017 which introduced machine learning techniques in string theory. This work made use of standard mach ine learning techniques\, including convolutional neural networks (CNN)\, in order to find new formulas for the minimum volume of Sasaki-Einstein ma nifolds corresponding to toric Calabi-Yau 3-folds. These geometries\, by t he AdS/CFT correspondence\, relate to a large class of $4d N=1$ supersymme tric gauge theories. The R-charges of the dual gauge theories are known to be related to the minimum volumes of the corresponding Sasaki-Einstein ma nifolds. In this talk\, we will review the process of volume minimization and give a short overview on ongoing work.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/11/ END:VEVENT BEGIN:VEVENT SUMMARY:David Schaich (University of Liverpool) DTSTART:20220518T081500Z DTEND:20220518T091500Z DTSTAMP:20260404T094752Z UID:NMTP2022/12 DESCRIPTION:by David Schaich (University of Liverpool) as part of Numerica l Methods in Theoretical Physics\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Piotr Sierant (ICFO) DTSTART:20220519T070000Z DTEND:20220519T080000Z DTSTAMP:20260404T094752Z UID:NMTP2022/13 DESCRIPTION:Title: POLFED - a new diagonalization approach to study non-equilibrium phenomena\nby Piotr Sierant (ICFO) as part of Numerical Methods in The oretical Physics\n\n\nAbstract\nI will describe polynomially filtered exac t diagonalization (POLFED) method of computing eigenvectors of large spars e matrices at arbitrary energies - a task that often arises when studying non-equilibrium phenomena in quantum many-body systems. The algorithm find s an optimal basis of a subspace spanned by eigenvectors with eigenvalues close to a specified energy target by a spectral transformation using a hi gh order polynomial of the matrix. The memory requirements scale much bett er with system size than in the state-of-the-art shift-invert approach\, w hile the total CPU time used by the two methods is similar. Also\, the per formance of POLFED is not severly impeded when the the number of non-zero elements in the matrix is increased allowing to efficiently study models w ith long-range interactions. A straightforward modification allows POLFED to investigate spectra of large Floquet unitary operators. I will demonstr ate the potential of POLFED examining many-body localization transition in 1D interacting quantum spin-1/2 chains.\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Snir Gazit (Hebrew University) DTSTART:20220519T081500Z DTEND:20220519T091500Z DTSTAMP:20260404T094752Z UID:NMTP2022/14 DESCRIPTION:Title: Unconventional criticality and Fermi-surface reconstruction witho ut symmetry breaking in a simple lattice model of gauge and matter fields. \nby Snir Gazit (Hebrew University) as part of Numerical Methods in Th eoretical Physics\n\n\nAbstract\nGauge theories play a central role in the theoretical description of unconventional phases of matter that go beyond the standard paradigms of quantum statistical mechanics. While in high-en ergy physics\, gauge fields correspond to fundamental particles\, in conde nsed matter theory they are typically emergent and are invoked as an effec tive description of the low-energy degrees of freedom. Notable examples in clude spin-liquids\, doped Mott insulators\, and the fractional Hall effec t\, among others. In my talk\, I will present a sign-problem free quantum Monte Carlo study of a lattice model hosting 'orthogonal' fermions coupled to an Ising-Higgs gauge theory. Our model provides a simple yet highly no n-trivial example of electron fractionalization\, which\, crucially\, rema ins numerically tractable. We uncover a particularly rich phase diagram ar ising from strong correlations between gauge and matter fields. In particu lar\, we find that in the background of pi-flux lattice an orthogonal semi -metal (OSM) forms with gapless Dirac fermion excitations. With the tuning of parameters\, the OSM undergoes a confinement transition\, in which sym metry breaking and confinement are coincident. We construct a field-theore tical description of the transition involving condensation of a matrix Hig gs field. The critical theory is predicted to sustain emergent and enlarg ed local (gauge) and global symmetries. We provide numerical evidence supp orting this prediction. We also find that the physical (gauge-neutral) sp ectral function in the OSM phase comprises four fermion pockets\, which sm oothly evolve to a 'large' Fermi surface upon approach to a Fermi liquid p hase. The reconstruction of the Fermi surface does not involve any form o f translational symmetry breaking\, in violation of the Luttinger sum rule .\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Masazumi Honda (Kyoto University) DTSTART:20220520T010000Z DTEND:20220520T020000Z DTSTAMP:20260404T094752Z UID:NMTP2022/15 DESCRIPTION:Title: Digital quantum simulation of higher-charge Schwinger model with topological term\nby Masazumi Honda (Kyoto University) as part of Nume rical Methods in Theoretical Physics\n\n\nAbstract\nI am going to talk abo ut application of quantum computation to numerical simulation of quantum f ield theory. Specifically we implement a digital quantum simulation of a gauge theory with a topological term in Minkowski spacetime\, which is pra ctically inaccessible by standard lattice Monte Carlo simulations. We focu s on 1+1 dimensional quantum electrodynamics with a topological term and a charge-q Dirac fermion known as the Schwinger model. We construct the tru e vacuum state of a lattice Schwinger model using adiabatic state preparat ion which\, in turn\, allows us to compute an expectation value of the fer mion mass operator with respect to the vacuum. \nUpon taking a continuum l imit we find that our result in massless case agrees with the known exact result. In massive case\, we find an agreement with mass perturbation theo ry in small mass regime and deviations in large mass regime. $\\\\$\nWe al so study a potential between heavy charged particles and see that the pote ntial changes its qualitative behavior as changing parameters: it shows co nfinement\, screening and an exotic behavior called negative tension behav ior in which particles with opposite charges repel with each other.\n\nRef s:$\\\\$\n[1] B.Chakraborty\, M. Honda\, T. Izubuchi\, Y. Kikuchi and A. Tomiya\, arXiv:2001.00485 $\\\\$\n[2] M. Honda\, E. Itou\, Y. Kikuchi\, L . Nagano and T. Okuda\, arXiv:2105.03276$\\\\$\n[3] M. Honda\, E. Itou\, Y. Kikuchi and Y. Tanizaki arXiv:2110.14105\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryo Hanai (APCTP) DTSTART:20220520T021500Z DTEND:20220520T031500Z DTSTAMP:20260404T094752Z UID:NMTP2022/16 DESCRIPTION:Title: Nonreciprocal phase transitions\nby Ryo Hanai (APCTP) as part of Numerical Methods in Theoretical Physics\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/NMTP2022/16/ END:VEVENT END:VCALENDAR