Alberto Sesana - Postdoctoral Scholar

Physical Address:

334D Whitmore Laboratory
University Park, PA 16802
Phone: +1.814.865.3390
Fax: +1.814.863.9608

Mailing Address:

The Pennsylvania State University
Department of Physics
104 Davey Laboratory
PMB 113
University Park, PA 16802

Research Interests

Gravitational Wave Sources

Gravitational Waves (GWs) are one of the most fascinating predictions of General Relativity. Though huge experimental efforts to detect gravitational waves have been made in the last twenty years, a direct GW detection has yet to come. In the next decade, different instruments should be capable of detecting gravitational waves and their sources such as the planned Laser Interferometer Space Antenna (LISA); the advanced ground base interferometer LIGOII and the ongoing and planned Pulsar Timing Arrays (PTAs) such as the Square Kilometer Array (SKA). Starting from current models of structure formation, I am working to quantify massive black hole (MBH) binaries (MBHB) and extreme/intermediate mass ratio inspirals (EMRI/IMRI) expected to be detected by LIGO/LISA, and I characterize the GW background in the ultra-low frequency domain (nHz) probed by PTAs, highlighting the capability of these instruments to place interesting constraints on the MBH assembly history.

Sketch of frequency domains probed by LISA and PTAs. Expected signals from SMBH binaries are shown: in the nHz regime the superposition of signals coming from a huge number of stationary sources would result in a stochastic background, while the mHz window would be spanned by single inspirals at a rate of few/yr.

Massive Black Hole Dynamics

I am also working to develop hybrid models (three body scattering experiment coupled with an analytical framework) to study the dynamics of MBHs and MBHBs in dense stellar environments (such as galactic nuclei). This topic is interesting from many points of view. For starters, the last stage of the MBHB path to coalescence is not yet well understood, and interaction with ambient stars may be an important physical process in driving the MBHB evolution. Secondly, 3-body ejections may be useful to explain the flat cores of elliptical galaxies. Lastly, MBHBs naturally eject hyper--velocity stars (HVSs) into galaxy halos, and the inspiral of an intermediate MBH onto SgrA (the MBH residing in the Milky Way center) is one of the mechanisms proposed to explain HVSs observed today in the Milky Way halo.