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BEGIN:VEVENT
SUMMARY:David Berenstein (UC Davis)
DTSTART;VALUE=DATE-TIME:20220516T010000Z
DTEND;VALUE=DATE-TIME:20220516T020000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220516T021500Z
DTEND;VALUE=DATE-TIME:20220516T031500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220516T070000Z
DTEND;VALUE=DATE-TIME:20220516T080000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220516T081500Z
DTEND;VALUE=DATE-TIME:20220516T091500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220517T010000Z
DTEND;VALUE=DATE-TIME:20220517T020000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220517T021500Z
DTEND;VALUE=DATE-TIME:20220517T031500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220517T070000Z
DTEND;VALUE=DATE-TIME:20220517T080000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220517T081500Z
DTEND;VALUE=DATE-TIME:20220517T091500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220518T010000Z
DTEND;VALUE=DATE-TIME:20220518T020000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220518T021500Z
DTEND;VALUE=DATE-TIME:20220518T031500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220518T070000Z
DTEND;VALUE=DATE-TIME:20220518T080000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220518T081500Z
DTEND;VALUE=DATE-TIME:20220518T091500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220519T070000Z
DTEND;VALUE=DATE-TIME:20220519T080000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220519T081500Z
DTEND;VALUE=DATE-TIME:20220519T091500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220520T010000Z
DTEND;VALUE=DATE-TIME:20220520T020000Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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;VALUE=DATE-TIME:20220520T021500Z
DTEND;VALUE=DATE-TIME:20220520T031500Z
DTSTAMP;VALUE=DATE-TIME:20230529T051757Z
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/
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