Negative modes and the thermodynamics of Reissner-Nordstr\"om black holes

We analyse the problem of negative modes of the Euclidean section of the Reissner-Nordstr\"om black hole in four dimensions. We find analytically that a negative mode disappears when the specific heat at constant charge becomes positive. The sector of perturbations analysed here is included in the canonical partition function of the magnetically charged black hole. The result obeys the usual rule that the partition function is only well-defined when there is local thermodynamical equilibrium. We point out the difficulty in quantising Einstein-Maxwell theory, where the so-called conformal factor problem is considerably more intricate. Our method, inspired by hep-th/0608001, allows us to decouple the divergent gauge volume and treat the metric perturbations sector in a gauge-invariant way.Comment: 24 pages, 1 figure; v2 minor changes to fit published versio

One-Dimensional Approximation of Viscous Flows

Attention has been paid to the similarity and duality between the Gregory-Laflamme instability of black strings and the Rayleigh-Plateau instability of extended fluids. In this paper, we derive a set of simple (1+1)-dimensional equations from the Navier-Stokes equations describing thin flows of (non-relativistic and incompressible) viscous fluids. This formulation, a generalization of the theory of drop formation by Eggers and his collaborators, would make it possible to examine the final fate of Rayleigh-Plateau instability, its dimensional dependence, and possible self-similar behaviors before and after the drop formation, in the context of fluid/gravity correspondence.Comment: 17 pages, 3 figures; v2: refs & comments adde

High and Low Dimensions in The Black Hole Negative Mode

The negative mode of the Schwarzschild black hole is central to Euclidean quantum gravity around hot flat space and for the Gregory-Laflamme black string instability. We analyze the eigenvalue as a function of space-time dimension by constructing two perturbative expansions: one for large d and the other for small d-3, and determining as many coefficients as we are able to compute analytically. Joining the two expansions we obtain an interpolating rational function accurate to better than 2% through the whole range of dimensions including d=4.Comment: 17 pages, 4 figures. v2: added reference. v3: published versio

Anomalies and Hawking radiation from the Reissner-Nordstr\"om black hole with a global monopole

We extend the work by S. Iso, H. Umetsu and F. Wilczek [Phys. Rev. Lett. 96 (2006) 151302] to derive the Hawking flux via gauge and gravitational anomalies of a most general two-dimensional non-extremal black hole space-time with the determinant of its diagonal metric differing from the unity ($\sqrt{-g} \neq 1$) and use it to investigate Hawking radiation from the Reissner-Nordstrom black hole with a global monopole by requiring the cancellation of anomalies at the horizon. It is shown that the compensating energy momentum and gauge fluxes required to cancel gravitational and gauge anomalies at the horizon are precisely equivalent to the $(1+1)$-dimensional thermal fluxes associated with Hawking radiation emanating from the horizon at the Hawking temperature. These fluxes are universally determined by the value of anomalies at the horizon.Comment: 18 pages, 0 figure. 1 footnote and 4 new reference adde

Singlet molecular oxygen-quenching activity of carotenoids: relevance to protection of the skin from photoaging

Carotenoids are known to be potent quenchers of singlet molecular oxygen [O2 (1Δg)]. Solar light-induced photooxidative stress causes skin photoaging by accelerating the generation of reactive oxygen species via photodynamic actions in which O2 (1Δg) can be generated by energy transfer from excited sensitizers. Thus, dietary carotenoids seem to participate in the prevention of photooxidative stress by accumulating as antioxidants in the skin. An in vivo study using hairless mice clarified that a O2 (1Δg) oxygenation-specific peroxidation product of cholesterol, cholesterol 5α-hydroperoxide, accumulates in skin lipids due to ultraviolet-A exposure. Matrix metalloproteinase-9, a metalloproteinase family enzyme responsible for the formation of wrinkles and sagging, was enhanced in the skin of ultraviolet-A -irradiated hairless mice. The activation of metalloproteinase-9 and the accumulation of 5α-hydroperoxide, as well as formation of wrinkles and sagging, were lowered in mice fed a β-carotene diet. These results strongly suggest that dietary β-carotene prevents the expression of metalloproteinase-9 (at least in part), by inhibiting the photodynamic action involving the formation of 5α-hydroperoxide in the skin. Intake of β-Carotene therefore appears to be helpful in slowing down ultraviolet-A -induced photoaging in human skin by acting as a O2 (1Δg) quencher

Direct measurements of beta-star in the Tevatron

Simultaneous turn-by-turn beam position measurements across collider detector long straight sections provide full phase space information of a free oscillation. For signals with enough coherence (typically 1-2000 revolutions) the amplitude function and its slope at the two BPM's can be directly measured. Results for the Tevatron low-{beta} regions with a few percent accuracy are described

Identifying a black hole X-ray transient in M31 with XMM-Newton and Chandra

Stochastic variability in two out of four XMM-Newton observations of XMMU J004303+4115 along with its power spectra and X-ray luminosities suggest a low-mass X-ray binary (LMXB) with a black hole primary. However, Chandra observations resolve the object into two point sources. We use data from 35 Chandra observations to analyse the contributions of each source, and attribute the variability to CXOM31 J004303.2+411528 (known as r2-3), which varies in intensity by a factor of ~100 between observations. We assume that the power density spectra of LMXBs are governed by the luminosity, and that the transition between types of power density spectra occurs at some critical luminosity in Eddington units, l_c, that applies to all LMXBs. We use results from these XMM-Newton observations and past results from the available literature to estimate this transition luminosity, and find that all results are consistent with l_c ~0.1 in the 0.3--10 keV band. CXOM31 J004303.2+411528 exhibits a low accretion rate power density spectrum at a 0.3--10 keV luminosity of (5.3+/-0.6)x10^{37} erg/s. Known stellar mass black holes have masses of 4--15 M_{\odot}; hence our observations of CXOM31 J004303.2+411528 are consistent with l_c ~0.1 if it has a black hole primary.Comment: Accepted for publication in A&A; 9 pages, 4 figure

Gregory-Laflamme instability of 5D electrically charged black strings

We study the Gregory-Laflamme instability of 5D compactified, electrically charged black strings. We consider static, linear perturbations of these solutions and derive master equation for these perturbations. Using numerical analysis we search for the threshold unstable modes and derive the critical wave-length. The results are illustrated in the black string mass v.s. electric charge phase diagram. Similar diagram is constructed using global thermodynamic equilibrium argument applied to the charged string and 5D electrically charged black hole. The results derived illustrate that electric charge makes the black string less stable.Comment: 8 pages, 2 figures; Some minor changes in the text. Added reference

Starbursts from strong compression of galactic molecular clouds due to the high pressure of the intracluster medium

We demonstrate that the high pressure of the hot intracluster medium (ICM) can trigger the collapse of molecular clouds in a spiral galaxy, leading to a burst of star formation in the clouds. Our hydrodynamical simulations show that the high gaseous (ram pressure and static thermal) pressure of the ICM strongly compresses a self-gravitating gas cloud within a short time scale ($\sim$ $10^{7}$ yr), dramatically increasing the central gas density, and consequently causing efficient star formation within the cloud. The stars developed in the cloud form a compact, gravitationally bound, star cluster. The star formation efficiency within such a cloud is found to depend on the temperature and the density of the ICM and the relative velocity of the galaxy with respect to it. Based on these results, we discuss the origin of starburst/poststarburst populations observed in distant clusters, the enhancement of star formation for galaxies in merging clusters, and the isolated compact HII regions recently discovered in the Virgo cluster.Comment: 13 pages and 3 figures (Fig.1 is color), accepted in ApJ

Thermodynamic and dynamical stability of Freund-Rubin compactification

We investigate stability of two branches of Freund-Rubin compactification from thermodynamic and dynamical perspectives. Freund-Rubin compactification allows not only trivial solutions but also warped solutions describing warped product of external de Sitter space and internal deformed sphere. We study dynamical stability by analyzing linear perturbations around solutions in each branch. Also we study thermodynamic stability based on de Sitter entropy. We show complete agreement of thermodynamic and dynamical stabilities of this system. Finally, we interpret the results in terms of effective energy density in the four-dimensional Einstein frame and discuss cosmological implications.Comment: 15 pages, 5 figures, REVTeX4; version accepted for publication in JCA