سمینار مشترک ذرات و کیهانشناسی  این هفته را  آقای دکتر روح الله محمدی از موزه علوم و فناوری ایران ارائه  خواهند کرد. عنوان و چکیدهٔ سمینار ایشان به شرح زیر است:

The generation of CMB B-mode polarization due to Compton scattering and any new interaction such as CMB -CNB interactions

Abstract: By approximately solving the first order of Quantum Boltzmann Equation for the density matrix of a photon ensemble, and time-evolution of Stokes parameters, we briefly show that how to add any new interaction in right side of Boltzmann equation. The magnetic-type of linear polarization, B-mode polarization, for the Cosmic Microwave Background cannot be generated by Compton scattering in the case of scalar mode of matter perturbations but this is possible to have B-mode in framework of the Compton scattering in the case of tensor mode of matter perturbations. For this reason, the ratio of tensor to scalar mode of matter perturbation, r-parameter, is estimated (at least for small $l$) by comparing the B-mode power spectrum with E-mode one $r\sim C_l^{BB}/C_l^{EE}$. We study the polarization of CMB specially B-mode polarization due to the weak interactions of Cosmic Neutrino Background (CNB) and CMB in additional to Compton scattering in both cases of scalar and tensor metric perturbations. In this framework, we show that B-mode polarization power spectrum $C_l^{BB}$ receives some contributions from the scalar and tensor modes which have significant effects on the value of r-parameter and also we show that B-mode polarization power spectrum can be used as indirectly detector for CNB which is very difficult to detect by using usual neutrino detectors.

این سمینار در روز سه شنبه ۱ دی ماه ۱۳۹۴، ساعت ۱۵ در تالار جناب (آمفی‌تئاتر دانشکده فیزیک) در زیرزمین  دانشکدهٔ فیزیک برگزار خواهد شد.