سمینار این هفته را خانم راضیه امامی از پژوهشکده فیزیک پژوهشگاه دانش های بنیادی  ( IPM) ارائه خواهند کرد. عنوان و چکیدهٔ سمینار ایشان به شرح زیر است:

خوشگی فسیل از امواج گرانشی اولیه در تورم ناهمسانگرد

 (Clustering Fossil from Primordial Gravitational Waves in Anisotropic Inflation)

Abstract: Inflationary models can correlate small-scale density perturbations with the long-wavelength gravitational waves (GW) in the form of the Tensor-Scalar-Scalar (TSS) bispectrum. This correlation affects the mass-distribution in the Universe and leads to the off-diagonal correlations of the density field modes in the form of the quadrupole anisotropy. Interestingly, this effect survives even after the tensor mode decays when it re-enters the horizon, known as the fossil effect. As a result, the off-diagonal correlation function between different Fourier modes of the density fluctuations can be thought as a way to probe the large-scale GW and the mechanism of inflation behind the fossil effect. Models of single field slow roll inflation generically predict a very small quadrupole anisotropy in TSS while in models of multiple fields inflation this effect can be observable. Therefore this large scale quadrupole anisotropy can be thought as a spectroscopy for different inflationary models. In addition, in models of anisotropic inflation there exists quadrupole anisotropy in curvature perturbation power spectrum. In this talk, we consider TSS in models of anisotropic inflation and show that the shape of quadrupole anisotropy is different than in single field models. In addition, in these models the quadrupole anisotropy is projected into the preferred direction and its amplitude is proportional to $g_* N_e$ where $N_e$ is the number of e-folds and $g_*$ is the amplitude of quadrupole anisotropy in curvature perturbation power spectrum. We use this correlation function to estimate the large scale GW as well as the preferred direction and discuss the detectability of the signal in the galaxy surveys like Euclid and 21 cm surveys.

این سمینار در روز یکشنبه ۱۷ خرداد ماه ۱۳۹۴، ساعت ۱۵ در کلاس فیزیک ۳ در طبقهٔ اول  دانشکدهٔ فیزیک برگزار خواهد شد.