119234273
Hawking radiation and near horizon universality of chiral Virasoro algebra
We show that the diffeomorphism anomaly together with the trace anomaly reveal a chiral Virasoro algebra near the event horizon of a black hole. This algebra is the same irrespective of whether the anomaly is covariant or consistent, thereby manifesting its universal character and the fact that only the outgoing modes are relevant near the horizon. Our analysis therefore clarifies the role of the trace anomaly in the diffeomorphism anomaly approach [Robinson and Wilczek in Phys. Rev. Lett. 95:011303, 2005; Iso et al. in Phys. Rev. Lett. 96:151302, 2006; Banerjee and Kulkarni in Phys. Rev. D 77:024018, 2008; Gangopadhyay and Kulkarni in Phys. Rev. D 77:024038, 2008] to the Hawking radiation.
119219712
Non-conformal hydrodynamics in Einstein-dilaton theory
A bstractIn the Einestein-dilaton theory with a Liouville potential parameterized by η, we find a Schwarzschild-type black hole solution. This black hole solution, whose asymptotic geometry is described by the warped metric, is thermodynamically stable only for 0 ≤ η < 2. Applying the gauge/gravity duality, we find that the dual gauge theory represents a non-conformal thermal system with the equation of state depending on η. After turning on the bulk vector fluctuations with and without a dilaton coupling, we calculate the charge diffusion constant, which indicates that the life time of the quasi normal mode decreases with η. Interestingly, the vector fluctuation with the dilaton coupling shows that the DC conductivity increases with temperature, a feature commonly found in electrolytes.
13913623
Hawking fluxes, back reaction and covariant anomalies
Starting from the chiral covariant effective action approach of Banerjee and Kulkarni (2008 Phys. Lett. B 659 827), 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 the effect of one-loop back reaction are obtained.
116599063
Hawking fluxes and covariant anomalies
A non-destructive, direct method and apparatus for producing stretch blow molded articles having at least one physical dimension within a preselected range. The apparatus includes an injection mold defining an injection mold interior surface having a first differentially dimensioned portion disposed at a preselected location thereon and capable of producing a parison having a parison exterior surface including a first marker formed by contact with the first differentially dimensioned portion, and a stretch blow mold defining a stretch blow mold interior surface having a second differentially dimensioned portion disposed at a predetermined location thereon and capable of producing the article from the parison including a second marker formed by contact with the second differentially dimensioned portion. Relative position of the first marker with respect to the second marker indicates whether a dimension is within a preselected range. The method includes injection molding a parison so that a parison exterior surface includes a first marker disposed at a preselected position thereon and formed by contact with a first differentially dimensioned portion disposed at a preselected location on an injection mold interior surface, and stretch blow molding an article from the parison so that an article exterior surface includes a second marker disposed at a predetermined position thereon and formed by contact with a second differentially dimensioned portion disposed at a predetermined location on a stretch blow mold interior surface.
119246679
Modified dispersion relations and the response of the rotating Unruh-DeWitt detector
We study the response of a rotating monopole detector that is coupled to a massless scalar field which is described by a nonlinear dispersion relation in flat spacetime. Since it does not seem to be possible to evaluate the response of the rotating detector analytically, we resort to numerical computations. Interestingly, unlike the case of the uniformly accelerated detector that has been considered recently, we find that defining the transition probability rate of the rotating detector poses no difficulties. Further, we show that the response of the rotating detector can be computed exactly (albeit, numerically) even when it is coupled to a field that is governed by a nonlinear dispersion relation. We also discuss the response of the rotating detector in the presence of a cylindrical boundary on which the scalar field is constrained to vanish. While superluminal dispersion relations hardly affect the standard results, we find that subluminal dispersion relations can lead to relatively large modifications.
118387184
Higher order WKB corrections to black hole entropy in brick wall formalism
We calculate the statistical entropy of a quantum field with an arbitrary spin propagating on the spherical symmetric black hole background by using the brick wall formalism at higher orders in the WKB approximation. For general spins, we find that the correction to the standard Bekenstein–Hawking entropy depends logarithmically on the area of the horizon. Furthermore, we apply this analysis to the Schwarzschild and Schwarzschild–AdS(dS) black holes and discuss our results.
1981738
Optical Observations of the Isolated Neutron Star RX J0720.4–3125
RX J0720.423125 is an unidentified bright, soft X-ray source that shows pulsations at an 8.39 s period and has a thermal spectrum. We present deep B- and R-band images of its X-ray localization. We find one possible counterpart in the X-ray error box, with magnitudes and . The very high B 5 26.6 5 0.2 R 5 26.9 5 0.3 X-ray‐to‐optical flux ratio confirms that this object is an isolated neutron star. We discuss possible models, and we conclude that only two are consistent with the data and at the same time are able to draw from a large enough population to make finding one nearby likely. In our opinion, the second criterion provides a stringent constraint but appears to have been ignored so far. The first model, suggested earlier, is that RX J0720.423125 is a weakly magnetized neutron star accreting from the interstellar medium. The second is that it is a relatively young, highly magnetized neutron star, a “magnetar,” which is kept hot by magnetic field decay.
18496422
THE QUIESCENT COUNTERPART OF THE SOFT GAMMA-RAY REPEATER SGR 0526 66
It is now commonly believed that soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are magnetars—neutron stars powered by their magnetic fields. However, what differentiates these two seemingly dissimilar objects is, at present, unknown. We present Chandra observations of RX J052600.3� 660433, the quiescent X-ray counterpart of SGR 0526� 66, famous for the intense burst of 1979 March 5. The source is unresolved at the resolution of Chandra. Restricting observations to a period range around 8 s, the period noted in the afterglow of the burst of 1979 March 5, we find evidence for a similar periodicity in two epochs of data obtained 20 months apart. The secular period derivative based on these two observations is 6:6ð5 Þ� 10 � 11 ss � 1 , similar to the period derivatives of the magnetars. As is the case with other magnetars, the spectrum is best fitted by a combination of a blackbody and a power law. However, quite surprisingly, the photon index of the power-law component is � � 3—intermediate to those of AXPs and SGRs. This continuum of C led us to suggest that the underlying physical parameter that differentiates SGRs from AXPs is manifested in the power-law component. Two decades ago, SGR 0526� 66 was a classical SGR, whereas now it behaves like an AXP. Thus, it is possible that the same object cycles between the SGR and AXP states. We speculate that the main difference between AXPs and SGRs is the geometry of the B fields, and this geometry is time dependent. Finally, given the steep spectrum of RX J052600.3� 660433, the total radiated energy of RX J052600.3� 660433 can be much higher than traditionally estimated. If this energy is supplied by the decay of the magnetic field, then the inferred B field of RX J052600.3� 660433 is in excess of 10 15 G, the traditional value for magnetars. Independent of this discussion, there could well be a class of neutron stars, 10 14 GdBd10 15 G, which are neither radio pulsars nor magnetars. Subject headings: pulsars: individual (SGR 0526� 66) — stars: neutron — X-rays: stars
14167939
Detecting Outer Planets in Edge-on Orbits: Combining Radial Velocity and Astrometric Techniques
The astrometric and radial velocity techniques of extrasolar planet detection attempt to detect the periodic reflex motion of the parent star by extracting this periodic signal from a time-sampled set of observations. The extraction is generally accomplished using periodogram analysis or the functionally equivalent technique of least-squares fitting of sinusoids. In this paper, we use a frequentist approach to examine the sensitivity of the least-squares technique when applied to a combination of radial velocity and astrometric observations. We derive an analytical expression for the sensitivity and show that the combined approach yields significantly better sensitivity than either technique on its own. We discuss the ramifications of this result to upcoming astrometric surveys with the Full-Sky Astrometric Mapping Explorer, the Keck Interferometer, and the Space Interferometry Mission.
10828298
SENSITIVE SEARCH FOR RADIO VARIABLES AND TRANSIENTS IN THE EXTENDED CHANDRA DEEP FIELD SOUTH
We report on an analysis of the Extended Chandra Deep Field South (E-CDFS) region using archival data from the Very Large Array, with the goal of studying radio variability and transients at the sub-milliJansky level. The 49 epochs of E-CDFS observations at 1.4 GHz sample timescales from 1 day to 3 months. We find that only a fraction (1%) of unresolved radio sources above 40 μJy are variable at the 4σ level. There is no evidence that the fractional variability changes along with the known transition of radio-source populations below 1 mJy. Optical identifications of the sources show that the variable radio emission is associated with the central regions of an active galactic nucleus or a star-forming galaxy. After a detailed comparison of the efficacy of various source-finding algorithms, we use the best to carry out a transient search. No transients were found. This implies that the areal density of transients with peak flux density greater than 0.21 mJy is less than 0.37 deg^(–2) (at a confidence level of 95%). This result is approximately an order of magnitude below the transient rate measured at 5 GHz by Bower et al. but it is consistent with more recent upper limits from Frail et al. Our findings suggest that the radio sky at 1.4 GHz is relatively quiet. For multi-wavelength transient searches, such as the electromagnetic counterparts to gravitational waves, this frequency may be optimal for reducing the high background of false positives.
14050044
Transients in the Local Universe
Two different reasons make the search for transients in the nearby Universe (d < 200 Mpc) interesting and urgent. First, there exists a large gap in the luminosity of the brightest novae (-10 mag) and that of sub-luminous supernovae (-16 mag). However, theory and reasonable speculation point to several potential classes of objects in this "gap". Such objects are best found in the Local Universe. Second, the nascent field of Gravitational Wave (GW) astronomy and the budding fields of Ultra-high energy cosmic rays, TeV photons, astrophysical neutrinos are likewise limited to the Local Universe by physical effects (GZK effect, photon pair production) or instrumental sensitivity (neutrino and GW). Unfortunately, the localization of these new telescopes is poor and precludes identification of the host galaxy (with attendant loss of distance and physical diagnostics). Both goals can be met with wide field imaging telescopes acting in concert with follow-up telescopes. Astronomers must also embark upon completing the census of galaxies in the nearby Universe.