829 research outputs found
Hawking Radiation from Charged Black Holes via Gauge and Gravitational Anomalies
Extending gr-qc/0502074, we show that in order to avoid a breakdown of
general covariance and gauge invariance at the quantum level the total flux of
charge and energy in each outgoing partial wave of a charged quantum field in a
Reissner-Nordstrom black hole background must be equal to that of a (1+1)
dimensional blackbody at the Hawking temperature with the appropriate chemical
potential.Comment: 4 pages, typos corrected, references added, version to appear in
Phys. Rev. Let
Hawking Fluxes, Back reaction and Covariant Anomalies
Starting from the chiral covariant effective action approach of Banerjee and
Kulkarni [Phys. Lett. B 659, 827(2008)], we provide a derivation of the Hawking
radiation from a charged black hole in the presence of gravitational back
reaction. The modified expressions for charge and energy flux, due to effect of
one loop back reaction are obtained.Comment: 6 pages, no figures, minor changes and references added, to appear in
Classical and Quantum Gravit
Joint Strong and Weak Lensing Analysis of the Massive Cluster Field J0850+3604
We present a combined strong and weak lensing analysis of the
J085007.6+360428 (J0850) field, which was selected by its high projected
concentration of luminous red galaxies and contains the massive cluster Zwicky
1953. Using Subaru/Suprime-Cam imaging and
MMT/Hectospec spectroscopy, we first perform a weak lensing shear analysis to
constrain the mass distribution in this field, including the cluster at and a smaller foreground halo at . We then add a strong
lensing constraint from a multiply-imaged galaxy in the imaging data with a
photometric redshift of . Unlike previous cluster-scale lens
analyses, our technique accounts for the full three-dimensional mass structure
in the beam, including galaxies along the line of sight. In contrast with past
cluster analyses that use only lensed image positions as constraints, we use
the full surface brightness distribution of the images. This method predicts
that the source galaxy crosses a lensing caustic such that one image is a
highly-magnified "fold arc", which could be used to probe the source galaxy's
structure at ultra-high spatial resolution ( pc). We calculate the mass
of the primary cluster to be with a concentration of , consistent with the mass-concentration relation of
massive clusters at a similar redshift. The large mass of this cluster makes
J0850 an excellent field for leveraging lensing magnification to search for
high-redshift galaxies, competitive with and complementary to that of
well-studied clusters such as the HST Frontier Fields.Comment: Accepted for publication in The Astrophysical Journal; 14 pages, 13
figures, 3 table
Anomalies, Hawking Radiations and Regularity in Rotating Black Holes
This is an extended version of our previous letter hep-th/0602146. In this
paper we consider rotating black holes and show that the flux of Hawking
radiation can be determined by anomaly cancellation conditions and regularity
requirement at the horizon. By using a dimensional reduction technique, each
partial wave of quantum fields in a d=4 rotating black hole background can be
interpreted as a (1+1)-dimensional charged field with a charge proportional to
the azimuthal angular momentum m. From this and the analysis gr-qc/0502074,
hep-th/0602146 on Hawking radiation from charged black holes, we show that the
total flux of Hawking radiation from rotating black holes can be universally
determined in terms of the values of anomalies at the horizon by demanding
gauge invariance and general coordinate covariance at the quantum level. We
also clarify our choice of boundary conditions and show that our results are
consistent with the effective action approach where regularity at the future
horizon and vanishing of ingoing modes at r=\infty are imposed (i.e. Unruh
vacuum).Comment: 21 pages, minor corrections, added an appendix to summarize our
notations for the Kaluza-Klein reductio
Magnetic glass in Shape Memory Alloy : Ni45Co5Mn38Sn12
The first order martensitic transition in the ferromagnetic shape memory
alloy Ni45Co5Mn38Sn12 is also a magnetic transition and has a large field
induced effect. While cooling in the presence of field this first order
magnetic martensite transition is kinetically arrested. Depending on the
cooling field, a fraction of the arrested ferromagnetic austenite phase
persists down to the lowest temperature as a magnetic glassy state, similar to
the one observed in various intermetallic alloys and in half doped manganites.
A detailed investigation of this first order ferromagnetic austenite (FM-A) to
low magnetization martensite (LM-M) state transition as a function of
temperature and field has been carried out by magnetization measurements.
Extensive cooling and heating in unequal field (CHUF) measurements and a novel
field cooled protocol for isothermal MH measurements (FC-MH) are utilized to
investigate the glass like arrested states and show a reverse martensite
transition. Finally, we determine a field -temperature (HT) phase diagram of
Ni45Co5Mn38Sn12 from various magnetization measurements which brings out the
regions where thermodynamic and metastable states co-exist in the HT space
clearly depicting this system as a 'Magnetic Glass'.Comment: Magnetic field tunes kinetic arrest and CHUF shows devitrification
and melting of Magnetic glas
The Cluster Lensing and Supernova Survey with Hubble (CLASH): Strong Lensing Analysis of Abell 383 from 16-Band HST WFC3/ACS Imaging
We examine the inner mass distribution of the relaxed galaxy cluster Abell
383 in deep 16-band HST/ACS+WFC3 imaging taken as part of the CLASH multi-cycle
treasury program. Our program is designed to study the dark matter distribution
in 25 massive clusters, and balances depth with a wide wavelength coverage to
better identify lensed systems and generate precise photometric redshifts. This
information together with the predictive strength of our strong-lensing
analysis method identifies 13 new multiply-lensed images and candidates, so
that a total of 27 multiple-images of 9 systems are used to tightly constrain
the inner mass profile, (r<160 kpc).
We find consistency with the standard distance-redshift relation for the full
range spanned by the lensed images, 1.01<z<6.03, with the higher redshift
sources deflected through larger angles as expected. The inner mass profile
derived here is consistent with the results of our independent weak-lensing
analysis of wide-field Subaru images, with good agreement in the region of
overlap. The overall mass profile is well fitted by an NFW profile with
M_{vir}=(5.37^{+0.70}_{-0.63}\pm 0.26) x 10^{14}M_{\odot}/h and a relatively
high concentration, c_{vir}=8.77^{+0.44}_{-0.42}\pm 0.23, which lies above the
standard c-M relation similar to other well-studied clusters. The critical
radius of Abell 383 is modest by the standards of other lensing clusters,
r_{E}\simeq16\pm2\arcsec (for z_s=2.55), so the relatively large number of
lensed images uncovered here with precise photometric redshifts validates our
imaging strategy for the CLASH survey. In total we aim to provide similarly
high-quality lensing data for 25 clusters, 20 of which are X-ray selected
relaxed clusters, enabling a precise determination of the representative mass
profile free from lensing bias. (ABRIDGED)Comment: 15 pages, 14 figures, 2 tabels; V3 matches the submitted version
later published in Ap
- âŠ