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10/07/24Seminario16:0017:001201 Dal PassoLeonardo Sangaletti University of Leipzig
Operator Algebras Seminar
An L4 quantum energy inequality for the thermal sector

Energy density and its positivity properties represent a fundamental subject in classical and quantum physics. In this talk, we will investigate this topic in the thermal representation of a free massive quantum scalar field. After a brief review of the fundamental mathematical tools at the base of this work, we will construct the GNS representation of our QFT induced by a state at thermal equilibrium (KMS). Therein, we will identify the generator of the time evolution and its spatial density. The symmetry between the "particles" and "holes" makes evident the impossibility for a lower bound for the expectation value of the energy density in this representation. In order to tackle this problem, we will investigate and extend some results of modular theory and non-commutative Lp spaces. In this way, we will obtain a general result concerning the expectation value of operators affiliated to a von Neumann algebra. Finally, the proven results will be applied to our setting to derive an L4 state dependent non-trivial QEI.

The Operator Algebra Seminar schedule is here:
09/07/24Seminario14:3015:301201 Dal PassoMaria Michaela PorzioSapienza Università di Roma
Seminario di Equazioni Differenziali
The role of the data on the regularity of the solutions to some non singular parabolic equations

In this talk we describe the influence of the initial data and the forcing terms on the regularity of the solutions to a class of evolution equations including the heat equation, linear and semilinear parabolic equations, together with the nonlinear p-Laplacian equation. We focus our study mainly on the regularity (in terms of belonging to appropriate Lebesgue spaces) of the gradient of the solutions.
NB:This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV CUP E83C23000330006
05/07/24Seminario16:0017:001201 Dal PassoPing XuU Penn State
ARTS Midsummer Day Edition
Derived differentiable manifolds

One of the main motivations behind derived differential geometry is to deal with singularities arising from zero loci or intersections of submanifolds. Both cases can be considered as fiber products of manifolds which may not be smooth in classical differential geometry. Thus, we need to extend the category of differentiable manifolds to a larger category in which one can talk about "homotopy fiber products". In this talk, we will discuss a solution to this problem in terms of dg manifolds. The talk is mainly based on a joint work with Kai Behrend and Hsuan-Yi Liao.
05/07/24Seminario14:3015:301201 Dal PassoMathieu StiénonU Penn State
ARTS Midsummer Day Edition
Formal geometry of groupoids

I will give a brief survey of the formal geometry of groupoids.
03/07/24Seminario16:0017:001201 Dal PassoVedran SohingerUniversity of Warwick
Operator Algebras and Mathematical Physics Seminar
Invariant measures as probabilistic tools in the analysis of nonlinear ODEs and PDEs

Gibbs measures for nonlinear dispersive PDEs have been used as a fundamental tool in the study of low-regularity almost sure well-posedness of the associated Cauchy problem following the pioneering work of Bourgain in the 1990s. In the first part of the talk, we will discuss the connection of Gibbs measures with the Kubo-Martin-Schwinger (KMS) condition. The latter is a property characterizing equilibrium measures of the Liouville equation. In particular, we show that Gibbs measures are the unique KMS equilibrium states for a wide class of nonlinear Hamiltonian PDEs. Our proof is based on Malliavin calculus and Gross-Sobolev spaces. This is joint work with Zied Ammari.
In the second part of the talk, we will explain a general principle that allows us to obtain almost sure global solutions for Hamiltonian PDEs provided that one has a stationary probability measure. In this context, stationarity refers to a solution of the associated Liouville equation. This more general notion replaces the invariance from before. The second part of the talk is joint work with Zied Ammari and Shahnaz Farhat.

Note: This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)

The Operator Algebra Seminar schedule is here:
21/06/24Seminario14:3015:301101 D'AntoniAdam Dor-onHaifa University
Operator Algebras Seminar
Arveson's hyperrigidity conjecture is false

A classical result in approximation theory due to Korovkin asserts that a sequence of positive unital maps on C([0,1]) converges pointwise to the identity if they merely converge to the identity on the functions 1,x,x^2. This result was later generalized by Saskin, who showed that convergence to the identity on a generating function system implies convergence to the identity everywhere if and only if the system has full Choquet boundary. Arveson's last open conjecture in his seminal work on non-commutative boundary theory predicts that a non-commutative analogue of Saskin's result holds. We refute Arveson's conjecture with an elementary counterexample. All notions will be explained during the talk.

The Operator Algebra Seminar schedule is here:
19/06/24Seminario16:0017:001201 Dal PassoNicola Pinamonti University of Genova
Operator Algebras Seminar
Secular growths and their relation to Equilibrium states in perturbative Quantum Field Theories

During this talk we discuss the emergence of secular growths in the correlation functions of interacting quantum field theories when treated with perturbation methods. It is known in the literature that these effects are present if the interaction Lagrangian density changes adiabatically in a finite interval of time. If this happens, the perturbative approach cannot furnish reliable results in the evaluation of scattering amplitudes or in the evaluation of various expectation values. We show, during this talk, that these effects can be avoided for adiabatically switched-on interactions, if the spatial support of the interaction is compact and if the background state is suitably chosen. In particular, this is the case when the background state is chosen to be at equilibrium and when thermalisation occurs at late time. The same result holds also if the background state is only invariant under time translation or if the explicit time dependence is not too strong, in a precise sense which will be discussed in the talk.

Note: This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)

The Operator Algebra Seminar schedule is here:
17/06/24Seminario15:0016:001201 Dal PassoTan Bui-ThanhUniversity of Texas at AustinLearn2Solve: A Deep Learning Framework for Real-Time Solutions of Forward, Inverse, and UQ Problems

Digital models (DMs) are designed to be replicas of systems and processes. At the core of a digital model (DM) is a physical/mathematical model that captures the behavior of the real system across temporal and spatial scales. One of the key roles of DMs is enabling “what if” scenario testing of hypothetical simulations to understand the implications at any point throughout the life cycle of the process, to monitor the process, to calibrate parameters to match the actual process and to quantify the uncertainties. In this talk, we will present various (faster than) real-time Scientific Deep Learning (SciDL) approaches for forward, inverse, and UQ problems. Both theoretical and numerical results for various problems including transport, heat, Burgers, (transonic and supersonic) Euler, and Navier-Stokes equations will be presented.
12/06/24Seminario16:0017:001201 Dal PassoKo SandersFAU Erlangen-Nuremberg
Operator Algebras Seminar
On distributions of positive type and applications to QFT

When quantum fields are represented as operators on a Hilbert space, their two-point distributions naturally give rise to distributions of positive type. A number of basic results on such distributions, especially for translation invariant two-point distributions, have been known for a long time. E.g., the Bochner-Schwartz Theorem fully characterises translation invariant distributions of positive type. In this talk I will present two apparently new results on distributions of positive type, one pertaining to pointwise products and the other to methods for cutting and pasting. Both results were motivated by physical questions and extend the toolbox of theoretical physics. I will present the results in a general mathematical context before discussing their applications to quantum energy inequalities and to separable states for a free scalar QFT.
07/06/24Seminario14:3015:301201 Dal Passo
Università del Piemonte Orientale
Algebra & Representation Theory Seminar (ARTS)
"Bundles on quantum projective varieties and their differential geometry"
N.B.: this talk is part of the activity of the MIUR Excellence Department Project Mat-Mod@TOV (CUP E83C23000330006)

  We study quantum principal bundles on projective varieties using a sheaf theoretic approach. Differential calculi are introduced in this context. The main class of examples is given by covariant calculi over quantum flag manifolds, which we provide via an explicit Ore extension construction. We next introduce principal covariant calculi by requiring a local compatibility of the calculi on the total sheaf, base sheaf and the structure Hopf algebra in terms of exact sequences. The examples of principal (covariant) calculi on the quantum principal bundles SLq(2,C) and GLq(2,C) over the projective space P1(C) are presented.

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