Research
Being especially fascinated by our Universe when it was young, I am interested in any aspects of this remote era. My research to date spans a wide range of times, from the period when the initial conditions for cosmic structure formation were created (during inflation) to the epoch when these seeds grew into the first stars.
During my Ph.D. I focused on the following projects:
Fluctuations in the 21-cm signal from the first stars
(read more).
Impact of the relative motion between the dark matter and the baryons on the first stars
(read more).
Pre-inflationary relics and their cosmological imprints
(read more).
Pre-inflationary relics and their cosmological imprints
Cosmological inflation is a "pre-historic" period of exponentially fast expansion which, among the rest, explains why do we see structure in the space (stars, galaxies, cluseters of galaxies etc): during the rapid expansion tiny scales are stretched to the size of cosmological scales, thus converting quantum fluctuations on tiny scales into classical on cosmologically large scales. The latter serve as initial conditions for the formation of cosmic structures through gravitational collapse.
In our work we consider a pre-inflationary world. Adding massive point particles to the simplest inflationary scenario (i.e., single field slow roll inflation), we explore the feedback of the post-inflationary Universe to this modification of the initial conditions. With a Pre-Inflationary Particle (PIP) the statistical isotropy of the observable Universe is broken, which would be a smoking gun for detection of such a relic. This would leave a corresponding imprint on all of the cosmological observables. For instance a pre-inflationary particle adds an anisotropic one-point function to the Cosmic Microwave Background (CMB) temperature anisotropies and ``tilts'' the space, creating a coherent flow of all the structure around. In Fialkov, Itzhaki & Kovetz (2010) we study imprints of PIP in the CMB and the large scale structure. In Rathaus, Fialkov & Itzhaki (2011) we explore gravitational lensing of the CMB by a "single lens" (e.g., formed by PIP).
Adding PIP is motivated on one hand by contemporary observations: e.g., missing angular power on large scales in the CMB and coherent bulk flow. On the other hand, existence of massive PIPs before inflation is a rather generic prediction of theories at high energy, e.g., magnetic monopoles predicted by grand unified theories. In addition, different types of pre-inflationary relics (particles, strings, domain walls) naturally arise in the framework of string theory. We have also studied imprints of a domain wall and a cosmic string in the CMB and the large scale structure.
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