|
Calendar of Physics Talks Vienna
| Infrared Finite Scattering Theory in QFT and Quantum Gravity |
| Speaker: | Gautam Satishchandran (Princeton University) |
| Abstract: | A long-standing problem in QFT and quantum gravity is the construction of an âIR-finite" S-matrix. In the gravitational case, the existence of these âinfrared divergencesâ is intimately tied to the âmemory effectâ (i.e. the permanent displacement of test masses due to the passage of a gravitational wave). In this talk, I shall explain the origin of these connections and illustrate that the construction of an IR-finite S-matrix requires the inclusion of states with memory (which do not lie in the standard Fock space). In massive QED an elegant solution to this problem was provided by Faddeev and Kulish who constructed an incoming/outgoing Hilbert space of charged particles âdressedâ with memory. We illustrate the ``preferred status'' of such states and their relationship to the superselection/decoherence structure of QED. However, we show that this construction fails [...] |
| Date: | Tue, 16.05.2023 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schrödinger-Hörsaal, (University of Vienna, Boltzmanngasse 5, 5th floor, Room Nr. 3500) |
| Contact: | D. Grumiller, S. Fredenhagen, E. Battista, R. Ruzziconi |
| Higher order resummation for LHC Higgs production |
| Speaker: | Matthew Lim (Univ. of Sussex) |
| Abstract: | It has been nearly eleven years since the announcement of the discovery of the Higgs boson, and since then many properties of the new particle have been established which seem to be consistent with the Standard Model prediction. The current precision of measurement in the Higgs sector in general,however,is only of the order of 10%. I will discuss improvements to the precision of resummed calculations in Soft-Collinear Effective Theory which aim to improve the state of affairs. I will first present results at N3LL'+aN3LO for the transverse momentum spectrum of the Higgs in heavy-quark initiated production, a process useful to constrain heavy quark Yukawa couplings. Secondly I will show predictions for jet veto resummation in the Higgs+jet process with NNLL'+NNLO uncertainties. These will facilitate comparison of theory with data via the Simplified Template Cross Section (STXS) framework. |
| Date: | Tue, 16.05.2023 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultaet fuer Physik, Erwin Schroedinger-HS, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, A. Broggio |
| Kite and Triangle diagrams through Symmetries of Feynman Integrals |
| Speaker: | Subhajit Mazumdar (Seoul National University) |
| Abstract: | The Symmetries of Feynman Integrals (SFI) is a method for evaluating Feynman Integrals which exposes a novel continuous group associated with the diagram which depends only on its topology and acts on its parameters. Using this method we study the kite diagram (a two-loop diagram with two external legs) and the most general triangle diagram (one-loop diagram with three external legs) with arbitrary masses and space-time dimensions. Generically, this method reduces a Feynman integral into a line integral over simpler diagrams. We identify the locus/loci in parameter space where the integrals further reduce to a mere linear combination of simpler diagrams. We generalize and revisit some known results. |
| Date: | Wed, 17.05.2023 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Sem.R. DA grun 02 C - GEO (2nd floor in the Freihaus, green tower) |
| Contact: | D. Grumiller, R. Ruzziconi |
| True Atomic-Resolution Surface Imaging under Ambient Conditions via Conductive Atomic Force Microscopy |
| Speaker: | Mehmet Z. Baykara (University of California Merced, Department of Mechanical Engineering, USA) |
| Abstract: | Atomic-scale characteristics of surfaces play a central role in numerous scientific fields. Yet, the tools utilized to characterize surfaces with atomic resolution rely on strict environmental conditions such as ultrahigh vacuum, limiting the relevance of results for realistic applications. Here, we report true atomic-resolution imaging via conductive atomic force microscopy (C-AFM) under ambient conditions [1]. Our approach delivers atomic-resolution maps on a variety of material surfaces that comprise defects including single atomic vacancies. Moreover, we report the capability of in situ charge state manipulation of defects on MoS2, and the observation of an exotic electronic effect: room-temperature charge ordering in a thin transition metal carbide (TMC) crystal (i.e., an MXene), α-Mo2C. Our findings herald the emergence of C-AFM as a powerful tool for atomic-resolution imaging and |
| Date: | Wed, 17.05.2023 |
| Time: | 16:00 |
| Location: | TU Wien, Institut für Angewandte Physik, E134 1040 Wien, Wiedner HauptstraÃe 8-10 Yellow Tower âBâ, 5th floor, SEM.R. DB gelb 05 A |
| Contact: | Univ. Prof. Dr. M. Valtiner |
| Clocks and the Thermodynamic Limits of Timekeeping |
| Speaker: | Paul Erker (TU Wien, Atominstitut) |
| Abstract: | The seminar will start with a short discussion on why a single ion on its own does not constitute a clock. We need clocks to measure time as quantum mechanics does not provide us with an observable for it. To be able to understand and investigate time measuring devices, we introduce a model of a clock, namely the autonomous quantum clock and show how thermodynamics limits its abilities to keep time, as well as the trade-off relations that follow. Next we present an experiment that hints at the fundamental nature of these trade-off relations and also discuss the connection of the quality of timekeeping to quantum computation. Some of the many open questions regarding clocks and the nature of time will be posed in the end. |
| Date: | Wed, 17.05.2023 |
| Time: | 16:15 |
| Duration: | 45 min |
| Location: | Hörsaal ATI |
| Contact: | Marcus Huber |
| Primordial black hole formation in $F(R)$ bouncing cosmology |
| Speaker: | Shreya Banerjee (Friedrich Alexander University) |
| Abstract: | The phenomenology of primordial black holes (PBHs) physics, and the
associated PBH abundance constraints, can be used in order to probe the
early-universe evolution. In this talk, we focus on the bounce realization within F(R) modified gravity and we investigate the corresponding PBH behavior. In
particular, we calculate the energy density power spectrum at horizon crossing time as a function of the involved theoretical parameters, and
then we extract the PBH abundance in the context of peak theory, considering
the critical collapse law for the PBH masses.
We calculate the PBH mass function, and the PBH abundance
at formation time as a function of the model
parameters, namely the bounce parameter and
the Hubble parameter at the transition time from
the bounce to the radiation dominated epoch. Upon full parameter analysis, we obtain very interesting constraints on the model |
| Date: | Wed, 17.05.2023 |
| Time: | 17:00 |
| Duration: | 60 min |
| Location: | TU Wien, Freihaus, Seminar room 7th floor, yellow area |
| Contact: | Benjamin Koch, Iva Lovrekovic |
|