119449490
A Rotating Kaluza-Klein black hole with squashed horizons
We find a rotating Kaluza-Klein black hole solution with squashed S-3 horizons in five dimensions. This is a Kerr counterpart of the charged one found by Ishihara and Matsuno [H. Ishihara, K. Matsuno, Kaluza-Klein black holes with squashed horizons. hep-th/0510094] recently. The space-time is geodesic complete and free of naked singularities. Its asymptotic structure is a twisted S' fiber bundle over a four-dimensional Minkowski space-time. We also study the mass and thermodynamics of this black hole. (c) 2006 Elsevier B.V. All rights reserved.
119235960
Note on Non-Gaussianities in Two-field Inflation
Two-field slow-roll inflation is the most conservative modification of a single-field model. The main motivations to study it are its entropic mode and non-Gaussianity. Several years ago, for a two-field model with additive separable potentials, Vemizzi and Wands invented an analytic method to estimate its non-Gaussianities. Later on, Choi et al. applied this method to the model with multiplicative separable potentials. In this note, we design a larger class of models whose non-Gaussianity can be estimated by the same method. Under some simplistic assumptions, roughly these models are unlikely able to generate a large non-Gaussianity. We look over some specific models of this class by scanning the full parameter space, but still no large non-Gaussianity appears in the slow-roll region. These models and scanning techniques would be useful for a future model hunt if observational evidence shows up for two-field inflation.
118153543
An oblique membrane paradigm for cosmological horizon
The membrane paradigm is a formalism for studying the event horizon of black holes. After analyzing it with some technical details and realizing it in the Reissner-Nordstrom black hole, we extend the paradigm to cosmological horizons. A standard membrane paradigm is established for the pure de Sitter horizon, and an oblique membrane paradigm is proposed for the trapping horizon of the Friedmann-Lemaitre-Robertson-Walker universe. In the latter case, the cosmological stretched horizon is oblique, thus the running of renormalization parameter is nonzero in the timelike direction and gives a correction to the membrane pressure. In this paradigm, the cosmological equations come from continuity equations of the membrane fluid and the bulk fluid respectively.
16941003
From N M2's to N D2's
In this short note, we reduce the N=6, U(N)xU(N) Chern-Simons gauge theories to N=8, U(N) Yang-Mills gauge theories. This process corresponds to recovering the world-volume theory of N D2-branes from that of N M2-branes in an intermediate energy range. The supersymmetries are enhanced because in this limit the branes localize far away from the orbifold singularity. Our main scheme is exactly in accordance with Mukhi and Papageorgakis's earlier work, although the Higgs mechanism becomes trickier in the present case. We also speculate on applying the scheme to a large class of new Bagger-Lambert models more generally.
119250105
M2-branes coupled to antisymmetric fluxes
By turning on antisymmetric background fluxes, we study how multiple M2-branes are coupled to them. Our investigation concentrates on the gauge invariance conditions for the Myers-Chern-Simons action. Furthermore, the dimensional reduction of M2-branes to D2-branes introduces more constraints on the newly introduced tensors. Particularly, for the theory based on A(4) algebra, we are able to fix all components of them up to an overall normalization constant. These results can not be simply obtained from the previously proposed cubic matrix representation for this algebra. We also comment on cubic matrices as the representations of 3-algebras.
118390460
1/R correction to gravity in the early universe
To explain the accelerated expansion of the late universe, the 1/R correction to Einstein gravity is usually considered, where R is the Ricci scalar. This correction term, if stable, is generally believed to be negligible during inflation. However, if the 1/R term is inflaton dependent, it will dramatically change the story of inflation. The entropy perturbation will naturally appear and drive the evolution of curvature perturbation outside the Hubble horizon. In a large class of models, the entropy perturbation can be made nearly scale invariant. In Einstein gravity the single-field inflation with a quartic potential has been ruled out by recent observations, but it revives when the 1/R term is turned on. The evolution of non-Gaussianities on a large scale are also studied and applied to inflation with 1/R correction. In some specific models, a large non-Gaussianity can be naturally generated outside the horizon. A recent study ruled out almost all f(R) models during the matter-dominated phase. Taking this into consideration, we are left with a limited class of model which recovers the Einstein gravity soon after reheating.
119218213
Four IRAC Sources with an Extremely Red H – [3.6] Color: Passive or Dusty Galaxies at z > 4.5?
We report the detection of four IRAC sources in the GOODS-South field with an extremely red color of H - [3.6] > 4.5. The four sources are not detected in the deep Hubble Space Telescope WFC3 H-band image with H-limit = 28.3 mag. We find that only three types of SED templates can produce such a red H -[3.6] color: a very dusty SED with the Calzetti extinction of A(V) = 16 mag at z = 0.8; a very dusty SED with the SMC extinction of AV = 8 mag at z = 2.0-2.2; and an 1 Gyr SSP with A(V) similar to 0.8 at z = 5.7. We argue that these sources are unlikely dusty galaxies at z 4.5 remains a possible solution for the 4 sources. At z > 4.5, these sources have stellar masses of log(M-*/M-circle dot) = 10.6-11.2. One source, ERS-1, is also a type-II X-ray QSO with L2-8 (keV) = 1.6 x 10(44) er gs(-1). One of the four sources is an X-ray QSO and another one is a HyperLIRG, suggesting a galaxy-merging scenario for the formation of these massive galaxies at high redshifts.
119181798
Radiative E1 decays of X(3872)
Abstract Radiative E1 decay widths of X ( 3872 ) are calculated through the relativistic Salpeter method, with the assumption that X ( 3872 ) is the χ c 1 ( 2 P ) state, which is the radial excited state of χ c 1 ( 1 P ) . We first calculated the E1 decay width of χ c 1 ( 1 P ) . The result is in agreement with experimental data excellently. Then we calculated the width of X ( 3872 ) with the assignment χ c 1 ( 2 P ) . Results are: Γ ( X ( 3872 ) → γ J / ψ ) = 33.0 keV , Γ ( X ( 3872 ) → γ ψ ( 2 S ) ) = 146 keV and Γ ( X ( 3872 ) → γ ψ ( 3770 ) ) = 7.09 keV . The ratio Br ( X ( 3872 ) → γ ψ ( 2 S ) ) / Br ( X ( 3872 ) → γ J / ψ ) = 4.4 agrees with experimental data by BaBar, but is larger than the new up-bound reported by Belle recently. With the same method, we also predicted the decay widths, Γ ( χ b 1 ( 1 P ) ) → γ ϒ ( 1 S ) = 30.0 keV , Γ ( χ b 1 ( 2 P ) ) → γ ϒ ( 1 S ) = 5.65 keV and Γ ( χ b 1 ( 2 P ) ) → γ ϒ ( 2 S ) = 15.8 keV , from which we get the full widths: Γ ( χ b 1 ( 1 P ) ) ∼ 85.7 keV and Γ ( χ b 1 ( 2 P ) ) ∼ 66.5 keV .
692665
Discovery of superstrong, fading, iron line emission and double-peaked balmer lines of the galaxy sdss j095209.56+214313.3: The light echo of a huge flare
We report the discovery of superstrong, fading, high-ionization iron line emission in the galaxy SDSS J095209.56+214313.3 (SDSS J0952+2143 hereafter), which must have been caused by an X-ray outburst of large amplitude. SDSS J0952+2143 is unique in its strong multiwavelength variability; such a broadband emission-line and continuum response has not been observed before. The strong iron line emission is accompanied by unusual Balmer line emission with a broad base, narrow core, and double-peaked narrow horns, and strong He II emission. These lines, while strong in the SDSS spectrum taken in 2005, have faded away significantly in new spectra taken in 2007 December. Comparison of SDSS, 2MASS, GALEX, and follow-up GROND photometry reveals variability in the NUV, optical, and NIR band. Taken together, these unusual observations can be explained by a giant outburst in the EUV-X-ray band, detected even in the optical and NIR. The intense and variable iron, helium, and Balmer lines represent the "light echo" of the flare, as it traveled through circumnuclear material. The outburst may have been caused by the tidal disruption of a star by a supermassive black hole. Spectroscopic surveys such as SDSS are well suited to detect emission-line light echoes of such rare flare events. Reverberation-mapping of these light echoes can then be used as a new and efficient probe of the physical conditions in the circumnuclear material in nonactive or active galaxies.
119247194
ON THE NATURE OF THE PROGENITOR OF THE Type Ia SN2011fe IN M101
The explosion of a Type Ia supernova, SN2011fe, in the nearby Pinwheel galaxy (M101 at 6.4 Mpc) provides an opportunity to study pre-explosion images and search for the progenitor, which should consist of a white dwarf (WD), possibly surrounded by an accretion disk, in orbit with another star. We report on our use of deep Chandra observations and Hubble Space Telescope observations to limit the luminosity and temperature of the pre-explosion WD. It is found that if the spectrum was a blackbody, then pre-SN WDs with steady nuclear burning of the highest possible temperatures and luminosities are excluded assuming moderate n{sub H} values, but values of kT between roughly 10 eV and 60 eV are permitted even if the WD was emitting at the Eddington luminosity. This allows the progenitor to be an accreting nuclear-burning WD with an expanded photosphere 4-100 times the WD itself, or a super-critically accreting WD blowing off an optically thick strong wind, or possibly a recurrent nova with luminosities an order of magnitude lower than Eddington. The observations are also consistent with a double degenerate scenario, or a spinning down WD that has been spun up by accretion from the donor.
119300428
Why X(3915) is so narrow as a $\chi_{c0}(2P)$ state
New resonance X(3915) was identified as the charmonium $\chi_{c0}(2P)$ by BABAR Collaboration, but there seems still open question of this assignment: why its full width is so narrow? To answer this question, we calculate the Okubo-Zweig-Iizuka (OZI) allowed strong decays $X(3915)\to D \bar D$, where X(3915) is assigned as a $\chi_{c0}(2P)$ state, and estimate its full width in the cooperating framework of $^3/!P_0^{}$ model and the Bethe-Salpeter (BS) method using the Mandelstam Formalism, during which non-perturbative QCD effects of the hadronic matrix elements are well considered by overlapping integral over the relativistic Salpeter wave functions of the initial and finial states. We find the node structure of $\chi_{c0}(2P)$ wave function resulting in the narrow width of X(3915) and show the dependence of the decay width on the variation of the initial mass of X(3915). We point out that the rate of $\frac{\Gamma(X(3915)\to D^+ D^-)}{\Gamma(X(3915)\to D^0 \bar D^0)}$ is crucial to confirm whether X(3915) is the $\chi_{c0}(2P)$ state or not.