Axion Inflation, GWs at interferometers and Primordial Black Holes (PBH)

Dr. Caner Ünal
Central European Institute for Cosmology and Fundamental Physics (CEICO),
Institute of Physics of the Czech Academy of Sciences

Axion inflation is well motivated for high energy models due to the fact that it enjoys a shift symmetry. This allows it potential to be protected from large quantum loop corrections, especially at high energies. The least irrelevant coupling with axion and gauge field , which is a FF_dual, could lead some interesting phenomenology including chiral GWs at CMB scales and even smaller scales. This interaction might also leave signatures in tensor (GWs at interferometers) and density fluctuations (PBH) at scales much smaller than CMB.

Yer     : MSGSÜ Bomonti Yerleşkesi, Fizik Bölümü, Lisansüstü Dersliği
Tarih : 12 Aralık 2019 Perşembe, 16:00

Gauge Invariance, Gravity and Dark Matter

Prof. Dr. Durmuş Ali Demir
Sabancı Üniversitesi

The Standard Model of elementary particles (SM) is a quantum field theory of color and electroweak interactions . It exists inherently in flat spacetime and lacks therefore gravity. It has no candidate for dark matter. The electric and color charges get explicitly broken through the quantum loops by the Poincare breaking scale. It will be shown in this talk that GR can emerge in a way securing the conservation of charge and color provided that there exists a beyond-SM sector (BSM) made up primarily of new massive fields. The BSM easily accounts for the current dark matter data as it does not have to couple to the SM. The dark matter must weigh below 400 GeV for possible SM-BSM couplings not to destabilize the Higgs mass.

Tarih: 05 Aralık 2019 Perşembe, Saat 16:00
Yer     : MSGSÜ Bomonti Yerleşkesi, Fizik Bölümü, Lisansüstü Dersliği

Geometric phases and the separation of the world

Sir Michael Berry
Melville Wills Professor of Physics (Emeritus),
Bristol Üniversitesi, İngiltere

The waves that describe systems in quantum physics can carry information about how their environment has been altered, for example by forces acting on them. This effect is the geometric phase. It also occurs in the optics of polarised light, where it goes back to the 1830s; and it gives insight into the spin-statistics relation for identical quantum particles. The underlying mathematics is geometric: the phenomenon of parallel transport, which also explains how falling cats land on their feet, and why parking a car in a narrow space is difficult. Incorporating the back-reaction of the geometric phase on the dynamics of the changing environment exposes the unsolved problem of how strictly a system can be separated from a slowly-varying environment, and involves different mathematics: divergent infinite series.

Tarih: 26 Kasım 2019 Salı, Saat 15:00
Yer : MSGSÜ Bomonti Yerleşkesi, Fizik Bölümü, Newton Dersliği

Renormalons in Quantum Mechanics

Cihan Pazarbaşı
Boğaziçi Üniversitesi
Fizik Bölümü

It is well known that renormalons are associated to divergences arises from the loop expansion of certain diagrams involving integration over logarithms. Although, renormalons were investigated in many QFT models, its non-perturbative nature remained unclear and the Borel resummation of the divergent expansion suffered from an infamous ambiguity. In this talk, after a brief introduction to the divergent perturbative expansions in quantum theories, I will investigate renormalon problem in the non-relativistic quantum mechanics with a potential contains 2D Dirac δ-potential, which requires renormalization, and an additional piece. We have discovered the existence of renormalon divergences for perturbative S-matrix, when the additional potential satisfies certain conditions. During the talk I will concentrate on a simple system, which gives us the full control on the calculations and allowed us to identify the non-perturbative contributions coming from the Borel resummation as the residue of the pole of the Green’s function associated to 2D Dirac δ-potential. In addition to that the Borel ambiguity is resolved by using the iε prescription, which fixed the sign of the non-perturbative contributions.

Tarih: 14 Kasım 2019 Perşembe, Saat: 16:00
Yer   :  MSGSÜ Fizik Bölümü, Lisansüstü Dersliği

Measurement of Strangely Beautiful Dimuons at CMS

Kai-Feng Chen
(Experimental High Energy Physics CMS Experiment at CERN, Geneva, Switzerland)

The measurement of the Bs to mu+mu- branching fraction and effective lifetime, and a search for the decay B0 to mu+mu- will be presented.
The analysis uses a data sample of pp collisions accumulated by the CMS experiment during LHC Run-1 and 2016. The branching fractions are determined by measuring the event yields relative to B+ to J/psi K+ decays with a reduction of the systematic uncertainties.
The decay Bs to mu+mu- has reached 5 sigma discovery significance, and the associated effective lifetime has been measured for the first time at CMS.

Yer     : MSGSÜ Bomonti Binası, Fizik Bölümü
Tarih : 12 Kasım 2019 Salı, 15:00

Nuclear Structure And Processes In The Relativistic Nuclear Energy Density Functional Theory

Nils Paar
University of Zagrep, Department of Physics

Complete understanding of how stellar evolution and nucleosynthesis work, with self-consistent microscopic description of all relevant
nuclear properties and phenomena included, has not been achieved yet. In particular, weak-interaction processes play a crucial role in the late stages of the evolution of a massive star and in presupernova stellar collapse, as well as in the synthesis of elements in the universe.  In order to provide a theoretical description of relevant nuclear properties and processes, a theory framework of the relativistic nuclear energy density functional (RNEDF) has been established including the relativistic Hartree-Bogoliubov model and relativistic quasiparticle random phase approximation, supplemented with modeling of the cross sections and rates of the weak interaction processes. Recent implementations of the RNEDF provide a unified description of a variety of nuclear properties of astrophysical relevance, including the equation of state, nuclear masses, collective excitations and weak interaction processes such as electron capture and neutrino induced reactions.

Yer: MSGSÜ Bomonti Binası, Fizik Bölümü
Tarih: 2 Ekim Çarşamba, Saat: 15:00

Not: Nils Paar 30 Ekim Pazartesi – 4 Eylül Cuma günleri arasında MSGSÜ Fizik Bölümünü ziyaret edecektir.