سمینار این هفته را خانم پانیذ پیکاری از  مرکز تحقیقات انرژی اتمی فرانسه بخش خدمات اخترفیزیک ساکله  ارائه خواهند کرد. عنوان و چکیدهٔ سمینار ایشان به شرح زیر است:

بازسازی پراکنده‌ٔ طیف توان اولیه

 (PRISM: Sparse Recovery of the Primordial Power Spectrum)

 

Abstract: The primordial power spectrum describes the initial perturbations in the Universe which eventually grew into the large-scale structure we observe today, and thereby provides an indirect probe of inflation or other structure-formation mechanisms. Here, we introduce a new method to estimate this spectrum from the empirical power spectrum of cosmic microwave background (CMB) maps.

A sparsity-based linear inversion method, coined PRISM, is presented. This technique leverages a sparsity prior on features in the primordial power spectrum in a wavelet basis to regularize the inverse problem. This non-parametric approach does not assume a strong prior on the shape of the primordial power spectrum, yet is able to correctly reconstruct its global shape as well as localized features. These advantages make this method robust for detecting deviations from the currently favored scale-invariant spectrum. We investigate the strength of this method on a set of WMAP 9-year simulated data for three types of primordial power spectra: a nearly scale-invariant spectrum, a spectrum with a small running of the spectral index, and a spectrum with a localized feature. This technique proves to easily detect deviations from a pure scale-invariant power spectrum and is suitable for distinguishing between simple models of the inflation. We process the WMAP 9-year and Planck PR1 data and find no significant departures from a nearly scale-invariant power spectrum. A high resolution primordial power spectrum can be reconstructed with this technique, where any strong local deviations or small global deviations from a pure scale-invariant spectrum can easily be detected.

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این سمینار در روز یکشنبه ۹ شهریور،  ساعت  ۸:۴۵ در اتاق شورا  در طبقهٔ پنجم دانشکدهٔ فیزیک برگزار خواهد شد.