Theoretical Astrophysics & Cosmology

In theoretical cosmology, significant advances are being made on the formation of the first structures in the universe, primordial star formation & gas chemistry , cosmological reionization , quasar absorption line models , simulations of the cosmic microwave background , the nature of the structures that produce Lyman-alpha forest lines in quasar spectra, the formation and evolution of galaxies using quasar absorption lines, the dynamics of interacting galaxy systems and dark matter, tidal disruption of globular clusters, description of the large scale structure of the Universe, the diffuse high energy background , and GRB as cosmological tools.   ( Abel, Charlton, Laguna, Meszaros).

In high energy theory, Penn State is a major center for the investigation of gamma-ray burst sources, including GRB physics , and cosmology with GRB and GRB spatial distribution models. Related areas are high-energy (TeV-EeV) neutrino astrophysics of GRB, AGN and other sources where hadron acceleration is expected to occur, and GRB gravitational wave physics questions. There are significant programs of research on compact gamma-and X-ray source models, black hole/agn models, diffuse high-energy radiation background , particle acceleration and high energy radiation processes (Meszaros, Pavlov , Sigurdsson ).

Penn State is also a major center of expertise on strongly magnetized neutron stars. There are active research programs on models of isolated neutron star atmospheres , accreting X-ray pulsar radiative transfer and beam/pulse shape models, physical processes in strongly magnetized plasmas , and interpretation of X- and gamma-ray observations of neutron stars ( Pavlov , Meszaros).

There are active programs combining observations with modeling of accretion disk atmosphere and mass/momentum transfer models of cataclysmic variable systems, spectrum and polarization of compact object accretion disks, model atmospheres of binary stars and pre-main sequence stars with disks, stellar activity in binaries, astro-seismology and planet detection, etc. (Wade, Eracleous, Feigelson, Ramsey).

Numerical relativity & astrophysics research is being done on black hole collisions, gravitational wave production in various astrophysical sources, including tidal disruption, and gamma-ray burst progenitors. Penn State is part of an international Grand Challenges collaboration aimed at developing numrical methods to accurately model space-time evolution in the strong field regime. A wide range of fundamental investigations in gravitational physics is being carried out on gravitational wave generation and detection, relativistic properties of neutron star systems. Research on millisecond pulsars and general relativistic phenomenology has achieved notable results in determining relativistic effects on binary pulsar orbits and planetary systems. Theoretical and numerical studies are being acrried out on the dynamics of galaxies and stellar systems, including systems with a central black hole, and implications for gamma-ray bursters, pulsars, star formation and planets. There is a related program of investigation of numerical and parallel programming methods. Much of this work is interdisciplinary, involving Astron. & Astrophysics, Physics and Mathematics faculty within the Center for Gravitational Physics and Geometry, and the NSF Physics Fronitier Center for Gravitational Wave Physics ( Laguna , Wolszczan, Sigurdsson, Meszaros, Finn).

Astrostatistics is an interdisciplinary area, developed jointly with members of the statistics department, which concentrates on the rigorous treatment of various statistical problems encountered in astronomy and astrophysics. Penn State has created and maintains an astrostatistics consulting center which is unique in the nation. (Feigelson).

Atomic and radiation processes are being investigated in various astrophysical environments, in particular quantum mechanical calculations of electron collision processes in high Z ions of relevance for supernova remnants and fusion, as well as plasma properties, atomic structure and transition probabilities in strongly magnetized plasmas (Pavlov ).