December 10
Speaker: Mina Aganagic, UC Berkley
Title: "Strings and Knots"
When: Monday, December 10, 2012, 11:00AM
Where: 831 Pupin Hall
December 18
Speaker: Timothy Arlen, University of California, Los Angeles
Title: "Intergalactic Magnetic Fields and Extreme TeV Blazars"
Abstract:
The intergalactic magnetic field (IGMF) can be indirectly probed through
its effect on electromagnetic cascades initiated by a source of
gamma-rays, such as active galactic nuclei (AGN). AGN that are
sufficiently luminous at TeV energies, “extreme TeV blazars” can produce
detectable levels of secondary radiation from inverse Compton (IC)
scattering of the electrons in the cascade, provided that the IGMF is
not too large. We review recent work in the literature which utilizes
this idea to derive constraints on the IGMF from three TeV-detected
blazars-1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also
investigate four other hard-spectrum blazars in the same framework.
Through a recently developed detailed three-dimensional Monte Carlo
code, incorporating all major effects of QED and cosmological expansion,
we research effects of major uncertainties such as the spectral
properties of the source, uncertainty in the UV - far IR extragalactic
background light (EBL), undersampled Very High Energy (VHE; energy >
100 GeV) coverage, and source-observer geometry. The implications of
these effects on the recently reported lower limits of the IGMF are
thoroughly examined to conclude that presently available data are
compatible with a zero IGMF hypothesis.
When: Tuesday, December 18, 2012, 11:30AM
Where: 705 Pupin Hall
December 19
Speaker: Ozlem Celik, NASA Goddard Space Flight Center
Title: "Intergalactic Magnetic Fields and Extreme TeV Blazars"
Abstract:
In its four years of operation, the Fermi LAT revolutionized our
understanding of pulsars with the detection of over 117 pulsars in
gamma-rays, more than an order of magnitude larger than the 7 pulsars
known at the end of CGRO era. These pulsars roughly/almost equally
populate three different sub-classes: young radio-loud pulsars, young
radio-quiet pulsars and radio-loud millisecond pulsars. Their pulse
profiles vary widely, and their spectra can be modeled by an
exponentially cutoff power law shape with a wide range of photon indices
and cutoff energies. It is of great interest to see how these observed
properties correlate with their intrinsic properties and what can be
deduced about high-energy pulsed emission mechanisms from these
observations. I will highlight some exciting recent results and
summarize what we are learning from the LAT observations of pulsars.
When: Wednesday, December 19, 2012, 10:00AM
Where: 705 Pupin Hall
