200 research outputs found
Higher Order Corrections to Black Hole Entropy
A scheme for calculating corrections to all orders to the entropy of any
thermodynamic system due to statistical fluctuations around equilibrium has
been developed. It is then applied to the BTZ black hole, AdS-Schwarzschild
black Hole and Schwarzschild black Hole in a cavity. The scheme that we present
is a model-independent scheme and hence universally applicable to all classical
black holes with positive specific heat. It has been seen earlier that the
microcanonical entropy of a system can be more accurately reproduced by
considering a logarithmic correction to the canonical entropy function. The
higher order corrections will be a step further in calculating the
microcanonical entropy of a black hole.Comment: 9 pages, Revised version to appear in Classical and Quantum Gravit
The Ysz--Yx Scaling Relation as Determined from Planck and Chandra
SZ clusters surveys like Planck, the South Pole Telescope, and the Atacama
Cosmology Telescope, will soon be publishing several hundred SZ-selected
systems. The key ingredient required to transport the mass calibration from
current X-ray selected cluster samples to these SZ systems is the Ysz--Yx
scaling relation. We constrain the amplitude, slope, and scatter of the Ysz--Yx
scaling relation using SZ data from Planck, and X-ray data from Chandra. We
find a best fit amplitude of \ln (D_A^2\Ysz/CY_X) = -0.202 \pm 0.024 at the
pivot point CY_X=8\times 10^{-5} Mpc^2. This corresponds to a Ysz/Yx-ratio of
0.82\pm 0.024, in good agreement with X-ray expectations after including the
effects of gas clumping. The slope of the relation is \alpha=0.916\pm 0.032,
consistent with unity at \approx 2.3\sigma. We are unable to detect intrinsic
scatter, and find no evidence that the scaling relation depends on cluster
dynamical state
Interpreting the strongly lensed supernova iPTF16geu: time delay predictions, microlensing, and lensing rates
We present predictions for time delays between multiple images of the
gravitationally lensed supernova, iPTF16geu, which was recently discovered from
the intermediate Palomar Transient Factory (iPTF). As the supernova is of Type
Ia where the intrinsic luminosity is usually well-known, accurately measured
time delays of the multiple images could provide tight constraints on the
Hubble constant. According to our lens mass models constrained by the {\it
Hubble Space Telescope} F814W image, we expect the maximum relative time delay
to be less than a day, which is consistent with the maximum of 100 hours
reported by Goobar et al. but places a stringent upper limit. Furthermore, the
fluxes of most of the supernova images depart from expected values suggesting
that they are affected by microlensing. The microlensing timescales are small
enough that they may pose significant problems to measure the time delays
reliably. Our lensing rate calculation indicates that the occurrence of a
lensed SN in iPTF is likely. However, the observed total magnification of
iPTF16geu is larger than expected, given its redshift. This may be a further
indication of ongoing microlensing in this system.Comment: 5 pages, 3 figures, 1 table, ApjL accepted, minor but important
correction
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