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:20260422T212752Z UID:NMTP2022/1 DESCRIPTION:Title: Aspects of the Quantum Mechanical Bootstrap\nby David Berenstein (UC Davis) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\n I will detail some recent advances in understanding how to solve one dimen sional quantum mechanical problems with the numerical Bootstrap method for problems in the real line\, the circle and the positive real axis. Numer ically\, convergence seems to be exponential in the real line and the posi tive real axis problem. For the circle problem\, one obtains the band stru cture of the potential. Finally\, I will describe some additional progress when dealing with Robin boundary conditions on the positive real axis pr oblem.\n LOCATION:https://researchseminars.org/talk/NMTP2022/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Robert de Mello Koch (University of Witwatersrand) DTSTART:20220516T021500Z DTEND:20220516T031500Z DTSTAMP:20260422T212752Z UID:NMTP2022/2 DESCRIPTION:Title: Numerical Loop Space for Multi-matrix systems\nby Robert de Mello Koc h (University of Witwatersrand) as part of Numerical Methods in Theoretica l Physics\n\n\nAbstract\nWe revisit the problem of solving multi-matrix qu antum mechanics\, at large $N$\, numerically. The approach adopted uses co llective field theory to give a loop space representation of the dynamics\ , leading to a constrained optimization problem. The constraint is solved using a master-field parametrization. The complete fluctuation spectrum is also computable in the above scheme\, and is of immediate physical releva nce. The numerical results presented prove that this approach solves\, by numerical loop space methods\, the general two matrix model problem.\n LOCATION:https://researchseminars.org/talk/NMTP2022/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Frank Pollmann (TUM) DTSTART:20220516T070000Z DTEND:20220516T080000Z DTSTAMP:20260422T212752Z UID:NMTP2022/3 DESCRIPTION:Title: Exploring Quantum Phases of Matter on Quantum Processors\nby Frank Po llmann (TUM) as part of Numerical Methods in Theoretical Physics\n\n\nAbst ract\nThe interplay of quantum fluctuations and interactions can yield nov el quantum phases of matter with fascinating properties. Particularly exci ting physics is at play when confining systems to two spatial dimensions. For this case it has been predicted that exotic quantum particles emerge —so-called “anyons”— that cannot exist in the three-dimensional wo rld we live in. Understanding the physics of such system is a very challen ging problem as it requires to solve quantum many body problems—which is generically exponentially hard on classical computers.\n\nIn this context \, universal quantum computers are potentially an ideal setting for simula ting the emergent quantum many-body physics. In my talk\, I will discuss h ow to use existing (noisy) quantum computers to simulate quantum phases of matter. First\, I will consider symmetry protected topological phases (S PT) in one-dimensional systems. For this case\, ground states of Hamiltoni ans can be obtained using shallow quantum circuits and we can observe a qu antum phase transition between different SPT phases on a quantum device. S econd\, we prepare the ground state of the toric code Hamiltonian in two-d imensions using an efficient quantum circuit on a superconducting quantum processor. We measure a topological entanglement entropy near the expected value of ln(2)\, and simulate anyon interferometry to extract the charact eristic braiding statistics of the emergent excitations.\n LOCATION:https://researchseminars.org/talk/NMTP2022/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Masanori Hanada (University of Surrey) DTSTART:20220516T081500Z DTEND:20220516T091500Z DTSTAMP:20260422T212752Z UID:NMTP2022/4 DESCRIPTION:Title: Black Hole from Matrices\nby Masanori Hanada (University of Surrey) a s part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nMatrix m odels can describe black hole via holography. I will review numerical appr oaches which were successful in the past\, and discuss the necessity of ne w methods for tackling certain fascinating problems.\n LOCATION:https://researchseminars.org/talk/NMTP2022/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Pietro Brighi (IST Austria) DTSTART:20220517T010000Z DTEND:20220517T020000Z DTSTAMP:20260422T212752Z UID:NMTP2022/5 DESCRIPTION:Title: Tensor network approaches to the study of the interplay of large localize d systems and small thermal grains\nby Pietro Brighi (IST Austria) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nIn isolate d quantum many-body systems\, thermalization is believed to occur due to t he ergodicity of the system. While most physical systems indeed behave in an ergodic way and their dynamics leads to thermal equilibrium\, some outs tanding counterexamples exist. Many-body localization (MBL) provides a par adigmatic case of ergodicity-breaking\, where strong disorder leads to the lack of relaxation to the thermal equilibrium.\n\nIn this talk I will pre sent recent studies of the interplay of large non-interacting localized ch ains and small ergodic baths. Using matrix product state (MPS) methods\, w e probe the dynamics of these systems\, showing that in the strong interac tion case not only the localized chain does not thermalize\, but it also l eads to the localisation of the bath\, a phenomenon known as MBL proximity effect. The presence of the thermal inclusion\, however\, leads to a dram atic change in the system\, as it makes the localized particles interact. As a consequence\, interesting entanglement patterns arise in the chain\, a feature we dubbed propagation of MBL. Thanks to a phenomenological theor y\, we are able to link the localisation of the thermal grain and the phen omenon of propagation of MBL\, reproducing the characteristic entanglement behavior.\n LOCATION:https://researchseminars.org/talk/NMTP2022/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Kazuki Yamamoto (Kyoto University) DTSTART:20220517T021500Z DTEND:20220517T031500Z DTSTAMP:20260422T212752Z UID:NMTP2022/6 DESCRIPTION:Title: Finite-size scaling in a non-Hermitian XXZ spin chain\nby Kazuki Yama moto (Kyoto University) as part of Numerical Methods in Theoretical Physic s\n\n\nAbstract\nIn recent years\, open quantum systems have been actively 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-Luttinger (TL) liquids by calculating correlation functions and performing finite-s ize scaling analysis of a non-Hermitian XXZ spin chain as a prototypical m odel in one-dimensional open quantum many-body systems [1]. Our analytic c alculation is based on effective field theory with bosonization\, finite-s ize scaling approach in conformal field theory\, and the Bethe-ansatz solu tion. Our numerical analysis is based on the density-matrix renormalizatio n group generalized to non-Hermitian systems (NH-DMRG). We uncover that th e model in the massless regime with weak dissipation belongs to the univer sality class characterized by the complex-valued TL parameter\, which is r elated to the complex generalization of the c=1 conformal field theory. As the dissipation strength increases\, the values of the TL parameter obtai ned by the NH-DMRG begin to deviate from those obtained by the Bethe-ansat z analysis\, indicating that the model becomes massive for strong dissipat ion. 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\, Masa ya Nakagawa\, Masaki Tezuka\, Masahito Ueda\, and Norio Kawakami\, arXiv:2 112.12467\, Phys. Rev. B in press.\n LOCATION:https://researchseminars.org/talk/NMTP2022/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Fabien Alet (CNRS) DTSTART:20220517T070000Z DTEND:20220517T080000Z DTSTAMP:20260422T212752Z UID:NMTP2022/7 DESCRIPTION:Title: Interior eigenvalue problem for localisable quantum lattice models in con densed matter\nby Fabien Alet (CNRS) as part of Numerical Methods in T heoretical Physics\n\n\nAbstract\nI will provide an overview of numerical techniques that have been proposed to obtain eigenstates deep in the middl e of the spectrum of many-body quantum systems. This problem is particular ly relevant for systems which do not follow the eigenstate thermalization hypothesis. I will discuss spectral transforms methods -- trying to revi ew different strategies and works --\, and focus in particular ont the shi ft-invert technique. Examples of applications in the field of many-body lo calization will also be presented. In conclusion\, perspectives will be gi ven on how to perhaps improve these methods and applications to other fiel ds.\n LOCATION:https://researchseminars.org/talk/NMTP2022/7/ END:VEVENT BEGIN:VEVENT SUMMARY:David Luitz (University of Bonn) DTSTART:20220517T081500Z DTEND:20220517T091500Z DTSTAMP:20260422T212752Z UID:NMTP2022/8 DESCRIPTION:Title: Krylov space time evolution and quantum typicality\nby David Luitz (U niversity of Bonn) as part of Numerical Methods in Theoretical Physics\n\n \nAbstract\nI will discuss how to perform exact time evolution of many-bod y wave functions using Krylov space algorithms. This method only relies on a fast matrix vector product of the Hamiltonian (or the evolution operato r) and is the only method which can deal with similarly large systems in t he regime of strong entanglement\, which is generically produced over time . In combination with the concept of quantum typically\, which allows us t o 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 long rang e interactions.\n LOCATION:https://researchseminars.org/talk/NMTP2022/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Raghav Jha (Perimeter Institute) DTSTART:20220518T010000Z DTEND:20220518T020000Z DTSTAMP:20260422T212752Z UID:NMTP2022/9 DESCRIPTION:Title: New approach to continuous spin models in two and three dimensions\nb y Raghav Jha (Perimeter Institute) as part of Numerical Methods in Theoret ical Physics\n\n\nAbstract\nWe apply tensor network methods to study the f amous phase transition in the two-dimensional $O(2)$ model and a generaliz ed version of this model that admits half-integer vortices in addition to the standard integer ones. We then consider the same model in three dimen sions and carry out the first tensor study and locate the continuous phas e transition. Furthermore\, we introduce finite chemical potential and exp lore the Silver Blaze phenomenon by computing the particle number density . While the addition of chemical potential leads to a non-real action and is not suited for the standard Monte Carlo\, it is straightforward to stu dy using tensors and presents itself as a strong contender over other nume rical methods.\n LOCATION:https://researchseminars.org/talk/NMTP2022/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Anosh Joseph (IISER Mohali) DTSTART:20220518T021500Z DTEND:20220518T031500Z DTSTAMP:20260422T212752Z UID:NMTP2022/10 DESCRIPTION:Title: Complex Langevin Simulations of Dynamical Symmetry Breaking in IKKT Matr ix Model\nby Anosh Joseph (IISER Mohali) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nIn this talk\, we report on the resu lts of complex Langevin simulations of the IKKT matrix model. This model i s conjectured to be a nonperturbative formulation of superstring theory in ten dimensions. Dynamical compactification of extra dimensions can be rea lized via spontaneous breaking of the model's SO(10) rotational symmetry. The phase of the Pfaffian in this model is inherently complex and thus can make Monte Carlo simulations unreliable. The complex Langevin method can handle wild fluctuations in the phase of the Pfaffian and give reliable re sults. Our preliminary simulation results point to dynamical symmetry brea king in the IKKT model.\n LOCATION:https://researchseminars.org/talk/NMTP2022/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Rak-Kyeong Seong (UNIST) DTSTART:20220518T070000Z DTEND:20220518T080000Z DTSTAMP:20260422T212752Z UID:NMTP2022/11 DESCRIPTION:Title: Machine Learning Calabi-Yau Volumes\nby Rak-Kyeong Seong (UNIST) as part of Numerical Methods in Theoretical Physics\n\n\nAbstract\nThe talk w ill give an overview of our work from 2017 which introduced machine learni ng techniques in string theory. This work made use of standard machine lea rning techniques\, including convolutional neural networks (CNN)\, in orde r to find new formulas for the minimum volume of Sasaki-Einstein manifolds corresponding to toric Calabi-Yau 3-folds. These geometries\, by the AdS/ CFT correspondence\, relate to a large class of $4d N=1$ supersymmetric ga uge theories. The R-charges of the dual gauge theories are known to be rel ated to the minimum volumes of the corresponding Sasaki-Einstein manifolds . In this talk\, we will review the process of volume minimization and giv e a short overview on ongoing work.\n LOCATION:https://researchseminars.org/talk/NMTP2022/11/ END:VEVENT BEGIN:VEVENT SUMMARY:David Schaich (University of Liverpool) DTSTART:20220518T081500Z DTEND:20220518T091500Z DTSTAMP:20260422T212752Z 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://researchseminars.org/talk/NMTP2022/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Piotr Sierant (ICFO) DTSTART:20220519T070000Z DTEND:20220519T080000Z DTSTAMP:20260422T212752Z UID:NMTP2022/13 DESCRIPTION:Title: POLFED - a new diagonalization approach to study non-equilibrium phenome na\nby Piotr Sierant (ICFO) as part of Numerical Methods in Theoretica l Physics\n\n\nAbstract\nI will describe polynomially filtered exact diago nalization (POLFED) method of computing eigenvectors of large sparse matri ces at arbitrary energies - a task that often arises when studying non-equ ilibrium phenomena in quantum many-body systems. The algorithm finds an op timal basis of a subspace spanned by eigenvectors with eigenvalues close t o a specified energy target by a spectral transformation using a high orde r polynomial of the matrix. The memory requirements scale much better with system size than in the state-of-the-art shift-invert approach\, while th e total CPU time used by the two methods is similar. Also\, the performanc e of POLFED is not severly impeded when the the number of non-zero element s in the matrix is increased allowing to efficiently study models with lon g-range interactions. A straightforward modification allows POLFED to inve stigate spectra of large Floquet unitary operators. I will demonstrate the potential of POLFED examining many-body localization transition in 1D int eracting quantum spin-1/2 chains.\n LOCATION:https://researchseminars.org/talk/NMTP2022/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Snir Gazit (Hebrew University) DTSTART:20220519T081500Z DTEND:20220519T091500Z DTSTAMP:20260422T212752Z UID:NMTP2022/14 DESCRIPTION:Title: Unconventional criticality and Fermi-surface reconstruction without symm etry breaking in a simple lattice model of gauge and matter fields.\nb y Snir Gazit (Hebrew University) as part of Numerical Methods in Theoretic al Physics\n\n\nAbstract\nGauge theories play a central role in the theore tical description of unconventional phases of matter that go beyond the st andard paradigms of quantum statistical mechanics. While in high-energy ph ysics\, gauge fields correspond to fundamental particles\, in condensed ma tter theory they are typically emergent and are invoked as an effective de scription of the low-energy degrees of freedom. Notable examples include s pin-liquids\, doped Mott insulators\, and the fractional Hall effect\, amo ng others. In my talk\, I will present a sign-problem free quantum Monte C arlo study of a lattice model hosting 'orthogonal' fermions coupled to an Ising-Higgs gauge theory. Our model provides a simple yet highly non-trivi al example of electron fractionalization\, which\, crucially\, remains num erically tractable. We uncover a particularly rich phase diagram arising f rom strong correlations between gauge and matter fields. In particular\, w e find that in the background of pi-flux lattice an orthogonal semi-metal (OSM) forms with gapless Dirac fermion excitations. With the tuning of par ameters\, the OSM undergoes a confinement transition\, in which symmetry b reaking and confinement are coincident. We construct a field-theoretical d escription of the transition involving condensation of a matrix Higgs fiel d. The critical theory is predicted to sustain emergent and enlarged loca l (gauge) and global symmetries. We provide numerical evidence supporting this prediction. We also find that the physical (gauge-neutral) spectral function in the OSM phase comprises four fermion pockets\, which smoothly evolve to a 'large' Fermi surface upon approach to a Fermi liquid phase. The reconstruction of the Fermi surface does not involve any form of trans lational symmetry breaking\, in violation of the Luttinger sum rule.\n LOCATION:https://researchseminars.org/talk/NMTP2022/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Masazumi Honda (Kyoto University) DTSTART:20220520T010000Z DTEND:20220520T020000Z DTSTAMP:20260422T212752Z UID:NMTP2022/15 DESCRIPTION:Title: Digital quantum simulation of higher-charge Schwinger model with topolog ical term\nby Masazumi Honda (Kyoto University) as part of Numerical M ethods in Theoretical Physics\n\n\nAbstract\nI am going to talk about appl ication of quantum computation to numerical simulation of quantum field th eory. Specifically we implement a digital quantum simulation of a gauge t heory with a topological term in Minkowski spacetime\, which is practicall y inaccessible by standard lattice Monte Carlo simulations. We focus on 1+ 1 dimensional quantum electrodynamics with a topological term and a charge -q Dirac fermion known as the Schwinger model. We construct the true vacuu m state of a lattice Schwinger model using adiabatic state preparation whi ch\, in turn\, allows us to compute an expectation value of the fermion ma ss operator with respect to the vacuum. \nUpon taking a continuum limit we find that our result in massless case agrees with the known exact result. In massive case\, we find an agreement with mass perturbation theory in s mall mass regime and deviations in large mass regime. $\\\\$\nWe also stud y a potential between heavy charged particles and see that the potential c hanges its qualitative behavior as changing parameters: it shows confineme nt\, screening and an exotic behavior called negative tension behavior in which particles with opposite charges repel with each other.\n\nRefs:$\\\\ $\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. Nagan o and T. Okuda\, arXiv:2105.03276$\\\\$\n[3] M. Honda\, E. Itou\, Y. Kiku chi and Y. Tanizaki arXiv:2110.14105\n LOCATION:https://researchseminars.org/talk/NMTP2022/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryo Hanai (APCTP) DTSTART:20220520T021500Z DTEND:20220520T031500Z DTSTAMP:20260422T212752Z UID:NMTP2022/16 DESCRIPTION:Title: Nonreciprocal phase transitions\nby Ryo Hanai (APCTP) as part of Num erical Methods in Theoretical Physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/NMTP2022/16/ END:VEVENT END:VCALENDAR