AVAN Jean
Classical r-matrix structure for the complex sine Gordon model.
The complete algebraic framework underlying the r-matrix structure associated
to the classical complex sine Gordon model is unraveled.
Slides.
Video.
BABENKO Constantin
One point functions of fermionic operators in the Super Sine Gordon model.
We describe the integrable structure of the space of local operators
for the supersymmetric sine-Gordon model.
Namely, we conjecture that this space is created by acting on the primary fields
by fermions and a Kac-Moody current.
We proceed with the computation of the one-point functions.
In the UV limit they are shown to agree with the alternative
results obtained by solving the reflection relations.
Based on arXiv 1905.09602.
Slides.
Video.
BELLIARD Samuel
Some recent advances in the Algebraic Bethe Ansatz
I will discuss a new way to calculate some scalar products from the algebraic
Bethe ansatz point of view.
In particular it allows to proves conjectures for a determinant form of the
scalar product for models without U(1) symmetries such as the closed/open XXX spin chain.
Slides.
Video.
BYKOV Dmitry
A new look at integrable sigma-models and their deformations.
I will show that integrable sigma-models with flag manifold target spaces,
as well as their (trigonometric/elliptic) deformations,
are chiral gauged bosonic Gross-Neveu systems.
The interactions are polynomial, and the cancellation of chiral anomalies is related
to the quantum integrability of the model.
Ricci-flow properties of the models are easily established at one loop.
Slides.
Video.
CANTINI Luigi
Boundary emptiness formation probabilities in the six-vertex model at Δ=1/2.
Since the seminal work of Razumov and Stroganov, we know that the ground state of
the XXZ spin chain at Δ=1/2, for specific boundary conditions, displays a rich
combinatorial content, several zero temperature correlation functions of this model have
(conjectural, and sometimes proven) closed exact formulas, even at finite size, often
involving enumerations of combinatorial objects such as Alternating Sign Matrices or
Plane Partitions. In this talk, after briefly reviewing some of the relevant background,
we shall present new results obtained in collaboration with C. Hagendorf and
A. Morin-Duchesne, concerning the overlap of those ground states with particular
factorized states. Such overlaps have a nice interpretation in terms of the six-vertex
model on a semi-infinite cylinder with free boundary conditions, as the expectation value
of a string of polarized edges at the edge of the cylinder.
Slides.
Video.
CRAMPE Nicolas
Free-Fermion entanglement and Leonard pairs.
I study the entanglement entropy for free-Fermion model. I
recall how it is related to the computation of the chopped correlation
matrix. Then, I present the construction of the algebraic Heun
operator which commutes with this correlation matrix and simplifies
the computation of its eigenvalues. I show why the concept of Leonard
pairs is important in this context.
Slides.
Video.
FRASSEK Rouven
Non-compact spin chains, stochastic particle processes and hidden equilibrium.
I will discuss the relation between non-compact spin chains studied in high energy
physics and the zero-range processes introduced by Sasamoto-Wadati, Povolotsky and
Barraquand-Corwin. The main difference compared to the standard SSEP and ASEP is
that in these models several particles can occupy one and the same site.
For the models with symmetric hopping rates I will introduce integrable boundary
conditions that are obtained from new solution to the boundary Yang-Baxter equation
(K-matrix). Finally, I will present an explicit mapping of the open SSEP
(and the non-compact model cousin) to equilibrium. It allows to obtain closed-form
solutions of the probabilities in steady state and of k-point correlations functions.
Slides.
Video.
GAMAYUN Oleksandr
Modeling finite entropy states with free fermions.
The behavior of dynamical correlation functions in one-dimensional quantum systems
at zero temperature is now very well understood in terms of linear and non-linear
Luttinger models. The "microscopic" justification of these models consists in exactly
accounting for the soft-mode excitations around the vacuum state and at most a few
high-energy excitations. At finite temperature, or more generically for finite entropy
states, this direct approach is not strictly applicable due to the different structure
of soft excitations. To address these issues we study asymptotic behavior of dynamic
correlation functions in one-dimensional free fermion models. On the one hand, we
obtain exact answers in terms of Fredholm determinants. On the other hand, based on
"microscopic" numerical resummations, we develop a phenomenological approach that
provides results depending only on the state-dependent dressing of the scattering phase.
Our main example will be the correlation function ix XY model.
Slides.
Video.
GÖHMANN Frank
Thermal form factor series for dynamical correlation functions
of the XXZ chain in the antiferromagnetic massive regime.
We consider the longitudinal dynamical two-point function of
the XXZ chain in the antiferromagnetic massive regime at zero
temperature. It has a series representation originating from
an expansion based on the form factors of the quantum transfer
matrix of the model. The series sums up multiple integrals which
can be interpreted in terms of multiple particle-hole excitations
of the quantum transfer matrix. In previous related works
the expressions for the form factor densities appearing under the integrals
were either presented as multiple integrals or in terms of
Fredholm determinants, even in the zero-temperature limit.
Here we obtain a representation which, in the zero-temperature
limit, involves only finite determinants of known special
functions. This will facilitate its further analysis.
Slides.
Video.
JIN Zizhuo Tony
Quantum exclusion processes.
Quantum exclusion processes constitute the natural generalization of classical
exclusion processes such as SSEP, ASEP and so on to the quantum realm.
Their equilibrium fluctuations entail a rich structure which accounts for
the quantum nature of the problem. I will introduce such quantum exclusion processes
and present recent results about their stationary properties.
Slides.
Video.
KOZLOWSKI Karol
Convergence of the form factor series in the quantum Sinh-Gordon model
in 1+1 dimensions.
I will discuss a technique allowing one to prove the convergence of form factor
expansion in the case of the simple massive quantum integrable field theory:
the Sinh-Gordon model.
Slides.
Video.
LEVKOVICH-MASLYUK Fedor
Separated variables and scalar products at any rank.
I will present new results in the program of developing the separation of variables
(SoV) approach for higher-rank integrable spin chains.
This method is expected to be very powerful but until recently it has been
little studied beyond the simplest rank-one cases.
I will describe how to solve the longstanding problem of deriving the scalar
product measure in separated variables for the su(N) and sl(N) models.
The results are based on constructing the SoV basis for both bra and ket states.
As a first application, I will derive new representations for a large class of
form factors.
Slides.
Video.
MALLICK Kirone
Exact solution for single-file diffusion.
A particle in a one-dimensional channel with excluded volume interaction
displays anomalous diffusion with fluctuations
scaling as t1/4 in the long time limit. This
phenomenon, seen in
various experimental situations, is called single-file diffusion.
In this talk, we shall present the exact formula for the
distribution
of a tracer and its large deviations in the one dimensional
symmetric simple exclusion process, a pristine model for
single-file diffusion, thus answering
a problem that has eluded solution for decades.
We use the
mathematical arsenal of integrable probabilities developed recently
to solve the one-dimensional Kardar-Parisi-Zhang
equation. Our results can be extended to situations where the system is
far from equilibrium, leading to a Gallavotti-Cohen
Fluctuation Relation and providing us with a highly nontrivial check
of the Macroscopic Fluctuation Theory.
Joint work with Takashi Imamura (Chiba) and Tomohiro Sasamoto (Tokyo).
Slides.
Video.
MEDENJAK Marko
Dissipative Bethe Ansatz: Exact Solutions of Quantum Many-Body Dynamics Under Loss.
I will discuss how to use Bethe Ansatz techniques for studying the properties of
certain systems experiencing loss. This will allow us to obtain the Liouvillian
spectrum of a wide range of experimentally relevant models.
Following the general discussion, I will address different aspects of the XXZ spin
chain experiencing loss at the single boundary.
Slides.
Video.
NICCOLI Giuliano
New quantum separation of variables for higher rank models.
I will describe our new quantum separation of variables method (SoV)
and I will consider as main example the rank 2 quantum integrable models.
Our SoV is based exclusively on the quantum integrable structure of the analyzed models
(i.e. their commuting conserved charges) to get their resolutions (spectrum and dynamics).
This is a distinguishing feature of it; indeed, others methods rely on some set of
additional requirements beyond integrability which may result in their reduced
applicability. Our main aim is to establish a method allowing to put on the same
footing the quantum integrability of a model and its effective solvability. Our SoV can
be reduced to the Sklyanin's SoV, if this last one applies, while it is proven to hold
for quantum integrable models for which Sklyanin's SoV or simple generalizations of it
do not apply, e.g. the higher rank models. SoV does not make any Ansatz and then the
completeness of the spectrum description is proven to be a built-in feature of it.
It can be seen as the natural quantum analogue of the classical separation of variables
in the Hamilton-Jacobi's theory, reducing multi-degrees of freedoms highly coupled
spectral problems into independent one-degree of freedom ones. Then the transfer
matrix wave functions are factorized into products of its eigenvalues (or of Baxter's
Q-operator eigenvalues) and our SoV should universally lead to determinant
representations of scalar products and even of form factors of local operators,
as we have already proven for several models solved by it.
Slides.
Video.
PROLHAC Sylvain
Riemann surfaces for KPZ fluctuations in finite volume.
The totally asymmetric simple exclusion process (TASEP) is a Markov process
described at large scales by KPZ universality. Bethe ansatz for height fluctuations of
TASEP with periodic boundary conditions is formulated in terms of meromorphic
differentials on a compact Riemann surface, which converges in the KPZ regime to
the infinite genus Riemann surface for half-integer polylogarithms.
For specific initial condition, the probability of the height can be interpreted as
a solution of the KdV equation assembling infinitely many solitons.
Slides.
Video.
SANTACHIARA Raoul
New bootstrap solutions in two-dimensional percolation models.
A very long standing problem is the determination of the Conformal Field Theories
that describe the continuum limit of non-local observables in two-dimensional statistical
model such as the connectivity properties of random Potts clusters.
In the last four years, a combination of 2D bootstrap approach, Temperlie-Lie
representation theory and numerical simulations has unveiled crucial
(and probably definitive) informations on these theories.
In this talk I present the state of art of this project, the questions that are
still open and, time allowing, some new lines of research.
Slides.
Video.
SCHEHR Gregory
Non-interacting trapped fermions: from GUE to multi-critical matrix models.
I will discuss a system of N one-dimensional free fermions in the presence of a
confining trap $V(x)$. For the harmonic trap $V(x) \propto x^2$ and at zero temperature,
this system is intimately connected to random matrices belonging to the Gaussian
Unitary Ensemble (GUE). In particular, the spatial density of fermions has, for large N,
a finite support and it is given by the Wigner semi-circular law. Besides, close to the
edges of the support, the spatial quantum fluctuations are described by the so-called
Airy-Kernel, which plays an important role in random matrix theory.
We will then focus on the joint statistics of the momenta, with a particular focus on the
largest one $p_{\rm max}$. Again, for the harmonic trap, momenta and positions play a
symmetric role and hence the joint statistics of momenta is identical to that of the
positions. Here we show that novel ``momentum edge statistics'' emerge when the
curvature of the potential vanishes, i.e. for "flat traps" near their minimum,
with $V(x) \sim x^{2n}$ and $n>1$. These are based on generalisations of the Airy kernel
that we obtain explicitly. The fluctuations of $p_{\rm max}$ are governed by new
universal distributions determined from the $n$-th member of the second Painlevé
hierarchy of non-linear differential equations, with connections to multi-critical
random matrix models, which have appeared, in the past, in the string theory literature.
Slides.
Video.
SERBAN Didina
The wave functions of the q-deformed Haldane-Shastry model.
The Haldane-Shastry chain is an unique example among the long-range integrable
spin chains, since it possesses Yangian symmetry for any length.
Although the construction of the eigenfunctions evades the usual Bethe Ansatz
procedure, these can be found due to their relation with Jack polynomials.
More than twenty years ago, a XXZ-like deformation of the Haldane-Shastry
model was also proposed, where the Yangian symmetry is replaced by quantum
affine symmetry. However, a similar construction for the (highest weight)
eigenfunctions was not available until recently.
In the talk I will report on these results, obtained in collaboration with
Jules Lamers and Vincent Pasquier, and I will comment on a set of open problems.
Slides.
Video.
VIGNOLI Louis
Separation of variables bases for integrable Y(gl(M|N)) models .
I will show how to construct quantum Separation of Variables (SoV) bases for the
fundamental inhomogeneous Y(gl(M|N)) supersymmetric integrable models with
quasi-periodic twisted boundary conditions. The SoV basis are constructed by
repeated action of the transfer matrix on a generic (co)vector. Diagonalizability and
non-degeneracy of the spectrum of the twist matrix is sufficient to guarantee the same
property for the transfer matrix. Eigenvalues are constrained to be solutions of a set
of functional equations, namely the fusion relations, supplemented by an inner-boundary
condition that arises from the representation theory of the underlying super-Yangian
symmetry. Eigenvectors are characterized by their wave functions, which have a
factorised form in the SoV basis.
As an application, I will treat the special case of the Y(gl(1|2)) model with
particular boundary conditions and compare it to usual Bethe Ansatz approaches.
Ref : arXiv:1907.08124v2
Slides.
Video.
ZADNIK Lenart
Inhomogeneous matrix product ansatz and exact steady states of boundary-driven
spin chains at large dissipation.
I will present a site-dependent Lax formalism allowing for an exact solution of
a dissipatively driven XYZ spin-1/2 chain in the limit of strong dissipation that
polarizes the boundary spins in arbitrary directions. The constituent matrices of
the ansatz for the steady state satisfy a simple linear recurrence that can be mapped
into an inhomogeneous version of the quantum group Uq(sl2) relations.
Slides.
Video.