Wydział Fizyki UW > Badania > Seminaria i konwersatoria > Exact Results in Quantum Theory

Exact Results in Quantum Theory

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Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Hélder Larraguível (IFT UW)

What can we learn from the topological recursion?

On this talk I plan to introduce de concept of topological recursion, as a solution to matrix models, and its current reformulation as a quantum Airy structure. Also point out some important applications and current research being conducted in this area.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Mateusz Szczygieł, Katarzyna Budzik (FUW)

Talk 1: Representations of SL(2,R)

Talk 2: Unitary representations of the universal cover of SL(2,R)

#1: My talk will focus on the theory of classical representations of SL(2,R). First I will present the representations of Lie algebra sl(2,R). Then I will present a transition from the representation of Lie algebra to the representation of Lie group, discussing possible problems in this procedure. This requires a brief discussion on the representations of universal cover of SL(2,R). With the knowledge of the action of Lie algebra representations I will derive conditions for the unitarity of SL(2,R) representations. At the end of my talk I will summarize the series of unitary representations of SL(2,R).

#2: The purpose of the talk will be to show that the three operators: the Schroedinger operator with inverse square potential, the dilation operator and operator of multiplication squared generate unitary representations of the universal cover of SL(2,R).

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Paweł Wójcik (FUW)

Geometry of the universal covering of SL(2, R)

I will present an introductory talk about the geometry of the universal covering of SL(2, R). I will first present SL(2, R) and I will show how this group can be interpreted as a surface. Then I will continue to the description of hyperbolas in 1 and 2 dimensions with the aim to give a general overview of how to think about elements of the group SL(2, R) which can be seen as points on a 3 dimensional hyperbola (or anti-de Sitter (AdS) space). I will present the algebra of SL(2, R) group and one parameter subgroups generated by them in SL(2, R). Then after introducing the KAN decomposition I will present how the idea of the universal cover emerges from it. I will conclude with presenting how the universal covering group can be imagined with the use of concepts previously introduced.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Jan Chwedeńczuk (IFT UW)

"Role of mode and particle entanglement in the violation of the Bell inequalities", część II

I will discuss the role of the mode and the particle entanglement in the observation of the violation of Bell inequalities in a genericsystem of massive particles. I will argue that in such configuration, the super-selection rules must be considered, which render a largevariety of quantum states to be effectively classical from the point of view of any Bell test of local realism.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Katja Sagerschnig (University of Vienna)

The geometry of almost Einstein (2,3,5) distributions

The first part of the talk will be a brief introduction to conformal tractor calculus, and to the construction of conformal structures associated with maximally non-integrable vector distributions on 5-manifolds. In the second part, I will report on joint work with Travis Willse on the geometry of such conformal structures admitting parallel standard tractors: A parallel standard tractor determines a partition of the manifold into several submanifolds, each naturally endowed with a geometric structure. This reveals links between (2,3,5) distributions and several other geometries, including, Sasaki-Einstein structures of signature (2,3), Fefferman-conformal structures, and their para-complex analogues.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Jerzy Lewandowski (IFT UW)

Quasi-local black hole theory

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Ehsan Hatefi (IFT UW)

Universality In string theory

We would like to introduce D-branes and make various remarks on string theory amplitudes and their relations to mathematics in type II string theory in which getting the exact and final form of the world sheet integrals up to five point mixed closed-open amplitudes to all orders are given.We are also going to to talk about all kinds of effective actions involving DBI, Chern-Simons and more importantly new Wess Zumino actions. Indeed we try to provide a comprehensive explanation even for D-brane-anti D-brane systems. We also introduce various new techniques to be able to derive all order α’ corrections to all type II super string effective actions. If time allows, we then mention several issues related to those effective actions as well.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Mateusz Szczygieł (WCh UW)

Discretization of the continuum state in the description of photoionization processes

The major problem of describing the photoionization of molecules and atoms is the continuum state of the ejected electron. We propose a method of approximating the Coulomb wavefunction in the finite basis set. The deviation of the potential resulting from the structure of ion can be taken into account in this method. We also propose the construction of the final state of the system for the simple case of He atom. Finally, we obtain the prescription for computing the photoionization cross section.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Daniel Siemssen (IFT UW)

Solving the Semiclassical Einstein Equation

I will present a novel approach towards solving the semiclassical Einstein equation in cosmological spacetimes. Different from previous approaches, this approach allows for arbitrary curvature coupling and full renormalization freedom. A main tool is an infinite-dimensional dynamical system for the regularized two-point function in the coincidence limit.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Kamil Serafin (IFT UW)

Renormalization of 1/r^2 potential

In quantum mechanics potential -g/r^2 is singular if the coupling constant g is too big. Therefore, to define a system with such a potential one needs to renormalize. I will present a simple application of a renormalization group procedure to the problem. As a result, we obtain a family of effective Hamiltonians which depend on the floating cutoff parameter. The family of Hamiltonians exhibits a rich structure with limit cycles, fixed points,triviality and asymptotic-freedom-like behaviors. I will also comment on more popular approaches to renormalization of 1/r^2 potential and argue the value of our approach.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Miłosz Panfil (IFT UW)

Edge singularities in non-equilibrium steady states: a study case of exotic states of matter

The singularities of the dynamical response function are one of the most remarkable effects in many-body critical one-dimensional systems. However these divergences exists only strictly at zero temperature. I will show that by joining two interacting Bose gases prepared either at different temperatures or chemical potentials, the non-equilibrium steady state (ness) emerging at large times around the junction displays edge singularities in the response function and quasi-long range order as would be expected for a critical ground state.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Maciej Kolanowski (FUW)

SYK model and beyond

AdS/CFT correspondence is conjecture about connections between conformal field theory in d dimensions and gravity with negative cosmological constant in (d+1) dimensions. Despite its huge popularity, it is not yet well understood because any test demands great deal of complicated calculations. As a result, people are tend to work on some low-dimensional toy models. I will discuss one of them – SYK model, theory which is supposed to be dual to 2-dimensional black hole spacetime. After that, we will focus on another (slightly non-equivalent) formulation of SYK model as Gurau—Witen theory which seems to be more natural one. Last but not least, we shall discuss recent generalization conjectured by Klebanov and proven in [1].Talk partially based on:[1] arXiv:1712.00249

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Dr hab. Michał P. Heller (Albert Einstein Institute, National Centre for Nuclear Research)

Towards Complexity for Quantum Field Theory States

The talk will follow up on the colloquium from the day before and discuss the quantum information notion of complexity in QFT settings. Based on 1707.08582 and upcoming works.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Vadim Belov (University of Hamburg)

On the 'volume simplicity' (and the ways towards it)

I recapitulate the status of the volume part of simplicity constraints in the EPRL-KKL model, and highlight the tension with their implementation (evidenced by non-geometric configurations in the asymptotics). I outline, at the level of the classical theory, the two main routes towards resolving this issue - in the quadratic or linear setting, respectively. Based on https://arxiv.org/abs/1708.03182, https://arxiv.org/abs/1710.06195

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Grzegorz Łach (IFT UW)

Four faces of the Casimir Effect

The Casimir Effect is one of the most direct manifestations of the quantum nature of the electromagnetic vacuum. Initially considered for an idealized, infinite, perfectly conducting parallel plates is now computed and measured for objects of complicated shapes and optical properties. I will present two recent formulations of the theory which make the calculation of the Casimir force possible in complex geometries.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Adam Bednorz (IFT UW)

Are we living in spaghetti?

12 years ago Xiao-Gang Wen proposed fermions and bosons as emergent states of loops and strings. We will discuss this idea, commenting its weakness, failures, and attempts to correct.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Andrea Dapor (FAU Erlangen)

Cosmological Effective Hamiltonian from full Loop Quantum Gravity

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Katarzyna Budzik (FUW)

Unitary representations of the Lorentz group

I will talk about unitary representations of SL(2,C) - the double covering group of the Lorentz group. In order to classify unitary representations, we will find all hermitian distributive functionals on the space of homogeneous functions which are invariant under the group action.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Paweł Duch (UJ)

Weak adiabatic limit in perturbative quantum field theory

In the talk I will present the recent results about the existence of the weak adiabatic limit in models of the perturbative quantum field theory with massless particles defined with the use of the Epstein-Glaser approach. One of the characteristic features of this approach is the use of a switching function in the intermediate steps of the construction of the scattering matrix and the interacting fields. A switching function plays the role of the infrared regularization and is removed by taking the adiabatic limit. In particular, in order to define the vacuum expectation values of the products or the time-ordered products of the interacting fields (called the Wightman and Green functions, respectively) one takes the so-called weak adiabatic limit.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Hironori Mori (IFT UW)

Comments on the Localization in Supersymmetric Gauge Theories

In this talk, I’d briefly review how the localization technique, an exact computational method, works in supersymmetric gauge theories, and comment on the developments due to the localization in the last decade. Moreover, I’ll introduce very recent results, which are ideas for my ongoing work, to reveal nontrivial relationship among quantum field theory, quantum algebra, quantum geometry, and quantum integrability.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Benjamin Bahr (University of Hamburg)

Knotted graphs and volume of four-dimensional polytopes

We discuss the imposition of the volume simplicity constraint in theEPRL spin foam model for quantum gravity, in particular, itsgeneralization to arbitrary vertices proposed by Kaminski, Kisielowskiand Lewandowski. As it turns out, this constraint is closely related tothe question of reconstruction of four-dimensional polytopes from theirface bivectors. We show how this can, in some cases, be formulated interms of knotting invariants of the boundary graphs, and discuss itsconnection to the non-geometricity modes of the model recently observedby some authors.

Zapraszamy do sali 1.40, ul. Pasteura 5 o godzinie 14:15

Wojciech Kamiński (IFT UW)