Oberseminar Mathematische Physik
im Wintersemester 2018/2019 von Prof. Dr. Detlef Dürr und
Prof. Dr. Dirk  AndrÃ© Deckert
The seminar is usually on Mondays, 16:15h, in room B133 starting on 22nd of October.
Organizer: Felix Haenle
News:
On Friday, 18.01.2019 our joint seminar with University of Regenburg takes place in Garching.
The schedule will be as follows:
1415 Michal Wrochna
1515:30 Break
15:3016:30 Daniela Cadamuro
16:3017:00 Break
17:0018:00 Lukas Nickel
18:30 Dinner in Garching, Greek Restaurant `Poseidonâ€™.
Menu
Talks
Date 
Room 
Title 
Speaker 

Mon 22.10.18, 16:15 
B133 
Qualitatively ergodicI will show that, given a region of overwhelming phase space measure (an equilibrium region in Boltzmann's sense) and a stationary measure, a system behaves qualitatively ergodic with respect to the equilibrium state, that is, almost all trajectories spend almost all of their time in equilibrium. 
Dr. Paula Reichert 
Mon 29.10.18, 16:15 
B133 
Scattering processes in the SpinBoson model as an application of Mourre theoryAn explicit formula for the oneboson scattering processes is derived in the massive SpinBoson model which describes the interaction between a twolevel atom coupling to a massive scalar field. The proof requires good control of the resolvent close to the real line which can be shown using Mourre theory.

Felix Haenle 
Mon 05.11.18, 16:15 
 
no seminar 
no seminar 
Mon 12.11.18, 16:15 
B133 
MultiTime formalism in a Quantum Field Theory ModelIn order to describe a QuantumNbody system in the Schrodinger picture in a
manifestly covariant way, one needs to introduce a separate time coordinate t_k
for each of the particles k = {1,...,N}. The wave function therefore depends on
N time coordinates (\MultiTime wave function") and the Schrodinger equation
becomes a system of N Partial Dierential Equations (PDEs). MultiTime wave
functions were already introduced in the 1930's and have become a topic of active
research again throughout the past years.
So far, a series of papers has been published, which investigate the existence and
uniqueness of solutions to the MultiTime Schrodinger equation systems appearing
in various quantum mechanical models. However, most of the considerations in
these papers were done on a nonrigorous level, for example by checking a certain
consistency condition. In my master thesis, I could establish a rigorous proof of
existence and uniqueness of a solution to the equations of motion for a Quantum
Field Theory (QFT) toy model. This talk will concern about MultiTime formalism
in general, how to construct a solution to the equations of motion and how to
show that this PDE system is actually solved. 
Sascha Lill 
Mon 19.11.18, 16:15 
B133 
cancelled 
Prof. Dr. Stefan Adams 
Mon 26.11.18, 16:15 
B133 
Counting in external field QED
Starting from the lift condition of unitary operators on Fock Space, I will derive an explicit formula for the lift of the oneparticle time evolution of Dirac particles subject to an external potential. 
Markus Noeth 
Mon 03.12.18, 16:15 
B133 
Yet another â€žproofâ€œ that something is wrong with Bohmian mechanicsI discuss the recent nogo theorem of Frauchiger and Renner based on an ``extended Wigner's friend'' thought experiment which is supposed to show that any singleworld interpretation of quantum mechanics leads to inconsistent predictions if it is applicable on all scales. I show that no such inconsistency occurs if one considers a complete description of the physical situation. I then discuss implications of the thought experiment that have not been clearly addressed in the original paper, including a tension between relativity and nonlocal effects predicted by quantum mechanics. My analysis applies in particular to Bohmian mechanics, showing that it provides a perfectly consistent description of the thought experiment. 
Dr. Dustin Lazarovici 
Mon 10.12.18, 16:15 
B133 
Direct interaction along light cones at the quantum level
Here I explain the idea that direct interactions along light cones, similar to the WheelerFeynman formulation of electrodynamics, can be implemented on the quantum level using integral equations for multitime wave functions. Multitime wave functions are wave functions psi(x_1,...,x_N) with N spacetime arguments x_i for N particles. The crucial point is that the N time variables of the x_i make it possible to express interactions with time delay, as relativity requires. Starting from the integral formulation of the nonrelativistic SchrÃ¶dinger equation, I derive a covariant integral equation as an evolution equation for psi, and discuss its mathematical structure. It is shown that the equation correctly reduces to the SchrÃ¶dinger equation with a Coulomb potential when time delay effects are neglected. The main mathematical results are existence and uniqueness theorems for a simplified version of the equation. This talk is partly about joint work with Roderich Tumulka.

Dr. Matthias Lienert 
Mon 17.12.18, 16:00 
B133 
On domain, selfadjointness, and spectrum of twobody Dirac operators with interaction
Interest in the mathematical treatment of twobody Dirac operators $H_{2BD}$, that describe two interacting electrons, arose from relativistic quantum chemistry. There, the existence of squareintegrable eigenfunctions of such operators is assumed without further justification. In this talk, we discuss a selfadjoint extension that is uniquely distinguished by means of finite potential energy. The difficulties we encounter are the unboundedness of $H_{2BD}$ from below, and that the interaction potential is not relatively bounded by the free Hamiltonian. If time allows, we also investigate the domain of $H_{2BD}$ and the possibility of infinite single particle kinetic energy states in this domain. 
Martin Oelker 
Mon 14.01.19, 16:15 
B133 
Indirect Measurements in Quantum Mechanics
We consider a quantum dot in a semiconductor device P and a train of probes sent to it. A projective
measurement is applied to each probe, just after it interacts with P. This produces a discrete densitymatrices valued
stochastic process rho_n. We prove that the density matrices, rho_n, purify as n tends to infinity. Our
results can be used to mathematically understand situations in the spirit of experiments of Haroche and Wineland
(which led to the Nobel Prize in Physics 2012).

Prof. Dr. Miguel Ballesteros 
Wed 23.01.19, 11:30 
Garching 
tba 
Prof. Dr. Howard Wiseman 
Mon 28.01.19, 16:15 
B133 
A functional central limit theorem for a dynamical system 
Anne Froemel 
Mon 04.02.19, 16:15 
B133 
The Cloud Chamber Problem in Bohmian Mechanics
The cloud chamber problem is the problem of the quantum mechanical description of the elementary particles' position detection in the Wilson cloud chamber.
In my talk I will quickly recapitulate what exactly the problem is, what has been done using standard quantum mechanics and why it is interesting and important to obtain the Bohmian description. Then I will talk about the recent progress we have made on the way towards it. 
Serj Aristarhov 