Day 32

Tuesday.  Parents leaving, start work in earnest.

1106.5886

DA white dwarfs in SDSS DR7 and search for infrared excess emission

Girven, Gaensicke, Steeghs, Koester

Select white dwarfs with hydrogen-rich atmospheres (DA WD) by SDSS photometry---95% complete, 62% efficiency (purity?).  g<=19 samples, found 4636 objects (+70% increase from Eisenstein+2006 for spectroscopic objects; x3 for photometry only objects).  For WD with >~80,000K, the spectro followup is 44% complete.  DA WD with lo-mass stellar companions or dusty debris discs via detection of excess near IR is about 2% of total (lower limit 0.8%).  ~1% are candidates for having dusty debris disc.

* Whoa, only 2%?  I guess there can be more larger-mass companions---for the sake of estimating SNIa progenitors (of the companion type, not double degenerate).

1106.6145
A new method for the determination of the growth rate from galaxy redshift surveys
Nusser, Branchini, Davis


From the redshift survey, determine mass distribution, calculate the peculiar velocity that depends on beta = f(Omega)/b, then apply that to the redshift, obtain expected absolute magnitude.  Compare with observed magnitude, and minimize the difference to constrain beta, the growth rate divided by bias.  For 2MASS survey, beta = 0.35 pm 0.1 at z~0.  Can work for surveys at z~1.  Independent from redshift space distortion in xi(s).  Provides check on alternative gravity models.


* independent constraint on beta, from a redshift survey with apparent magnitudes.


1106.5493
Dark Matter and synchrotoron emission from galactic center radio filaments
Linden, Hoooper, Yusef-Zadeh


A 5-10 GeV DM particle annihilation producing e-e+ pairs can give consistent signal with the hard synchrotron radiation coming from non-thermal radio filaments (NRFs)--intensity, spectral shape, flux variation.  The radio filaments are due to the magnetic field lines, whose origin is unknown.  The characteristics of DM particle can also give consistent results with the excess gamma-ray observed from the galactic center by Fermi-LAT, CoGeNT and DAMA/LIBRA.


* An interesting scenario that seems to work well.

1106.5943

SMBH Formation via gas accretion in nuclear stellar clusters

Davies, Miller, Bellovary

How did SMBH form in the early universe (z>6)?  Suggest: dense star cluster contracted at timescales affected by nearly free-fall inflow of self-gravitating gas with mass comparable or larger than the star cluster.  Cluster goes into a period of homologous core collapse; high central density for fast mergers of stellar-mass BHs, and a rapid production of 1e5 M_sun or larger BG.


* Where is the DM in this picture of SMBH formation?


1106.6025
Chaotic inflation and supersymmetry breaking
Kallosh, Linde, Olive, Rube


Chaotic inflation models in supergravity with arbitrary inflaton potential.  Include matter fields in the visible sector (?), employ SUSY breaking based on a particular phenomenological version of KKLT mechanism (?).  Describe specific features of reheating in this class of models, and show how to solve cosmological moduli (?) and gravitino problems in this context.


* reheating mechanism!  Ooh, I've never seen a specific theory mentioned before.


1012.0583
Constraining the stellar mass function in the galactic center via mass loss from stellar collisions
Rubin, Loeb


Calculate mass loss rate due to dynamical stellar interactions at galactic center: >1e-5 M_sun/yr in the vicinity of ~1" today.  dN/dM ~ M^{- alpha}, where alpha >~ 1.25.  Constrain initial mass function of the galactic center, depending on star formation scenarios.


* similar to van Putten's stellar cluster evaporation, except done in galaxy-core scales.


1106.4005
Direct stau production at hadron colliders in cosmologically motivated scenarios
Lindert, Steffen, Trenkel

Calculate dominant stau pair production at hadron colliders--b-quark annihilation and gluon fusion can enhance cross sections by more than x10 wrt Drell-Yan predictions.  Propose collider test of cosmologically motivated scenarios.

* okay, didn't get that one very well.