118255950
Classical stability of black D3-branes
We have investigated the classical stability of charged black D3-branes in the type-IIB supergravity under small perturbations. For s-wave perturbations it turns out that black D3-branes are unstable when they have small charge density. As the charge density increases for given mass density, however, the instability decreases down to zero at a certain finite value of the charge density, and then black D3-branes become stable all the way down to the extremal point. It has also been shown that such critical value at which its stability behavior changes agrees very well with the predicted one by the thermodynamic stability behavior of the corresponding black hole system through the Gubser-Mitra conjecture. Unstable mode solutions we found involve non-vanishing fluctuations of the self-dual five-form field strength. Some implications of our results are also discussed.
119451627
Dark energy, inflation and the cosmic coincidence problem
Abstract We show that holographic dark energy could explain why the current dark energy density is so small, if there was an inflation with a sufficient expansion in the early universe. It is also suggested that an inflation with the number of e-folds N ≃ 65 may solve the cosmic coincidence problem in this context. Assuming the inflation and the power-law acceleration phase today we obtain approximate formulas for the event horizon size of the universe and dark energy density as functions of time. A simple numerical study exploiting the formula well reproduces the observed evolution of dark energy. This nontrivial match between the theory and the observational data supports both inflation and holographic dark energy models.
118494859
Gravity from quantum information
We suggest that the Einstein equation can be derived from Landauer’s principle applied to an information erasing process at a local Rindler horizon and Jacobson’s idea linking the Einstein equation with thermodynamics. When matter crosses the horizon, information on the matter disappears, and the horizon entanglement entropy increases to compensate for the entropy reduction. The Einstein equation describes an information-energy relation during this process, which implies that entropic gravity is related to the quantum entanglement of the vacuum and has a quantuminformation theoretic origin.
15236719
Global and local D-vortices
Codimension-two objects on a system of brane-antibrane are studied in the context of Born-Infeld type effective field theory with a complex tachyon and U(1) × U(1) gauge fields. When the radial electric field is turned on in D2 ¯ D2, we find static regular global and local D-vortex solutions which could be candidates of straight cosmic D-strings in a superstring theory. A natural extension to DF-strings is briefly discussed.
119306084
An efficient representation of Euclidean gravity I
A bstractWe explore how the topology of spacetime fabric is encoded into the local structure of Riemannian metrics using the gauge theory formulation of Euclidean gravity. In part I, we provide a rigorous mathematical foundation to prove that a general Einstein manifold arises as the sum of SU(2)L Yang-Mills instantons and SU(2)R anti-instantons where SU(2)L and SU(2)R are normal subgroups of the four-dimensional Lorentz group Spin(4) = SU(2)L × SU(2)R. Our proof relies only on the general properties in four dimensions: The Lorentz group Spin(4) is isomorphic to SU(2)L × SU(2)R and the six-dimensional vector space Λ2T∗M of two-forms splits canonically into the sum of three-dimensional vector spaces of self-dual and anti-self-dual two-forms, i.e., $ {\Lambda^2}{T^{ * }}M = \Lambda_{ + }^2 \oplus \Lambda_{ - }^2 $. Consolidating these two, it turns out that the splitting of Spin(4) is deeply correlated with the decomposition of two-forms on four-manifold which occupies a central position in the theory of four-manifolds.
17263525
ON WILSON SURFACES IN TOPOLOGICAL CHERN-SIMONS INTERACTION IN 3+1 DIMENSIONS
We comment on the regularization of the expectation values of Wilson surfaces for the bosonic string in 3+1 dimensions. We analyze the singular behaviors of propagators for the Chern-Simons action with the additional higher order terms.
119122873
Longitudinal top polarization as a probe of a possible origin of forward–backward asymmetry of the top quark at the Tevatron
Abstract If the forward–backward (FB) asymmetry of top quark ( A FB ) observed at the Tevatron deviates from the SM prediction, there must be P -violating interactions in q q ¯ → t t ¯ . This new interaction will necessarily affect the top spin polarization. In this Letter, we perform a model independent analysis on the longitudinal (anti)top polarization ( P L and P ¯ L ) using an effective lagrangian with dim-6 four-quark operators relevant for q q ¯ → t t ¯ , and show that the P -odd observable corresponding to the polarization difference ( P L − P ¯ L ) gives important informations on the chiral structures of new physics that might be relevant to the A FB .
465148
SUPERGRAVITY RADIATIVE EFFECTS ON SOFT TERMS AND THE MU TERM
We compute quadratically divergent supergravity one-loop effects on soft supersymmetry-breaking parameters and the $\mu$ term in generic hidden sector supergravity models. These effects can significantly modify the matching condition for soft parameters at the Planck scale and also provide several new sources of the $\mu$ term which are naturally of order the weak scale. We also discuss some phenomenological implications of these effects, particularly the violation of the scalar mass universality which may lead to dangerous FCNC phenomena, and apply the results to superstring effective supergravity models.
118662023
Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics
A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.
118544704
Measuring the Higgs boson mass with transverse mass variables
We provide a comparative study of the Higgs boson mass measurements based on two approaches to the dileptonic decay of W bosons produced by the Higgs boson decay, one using the kinematic variable M true T and the other using the M T2 -assisted on-shell reconstruction of the invisible neutrino momenta. We find that these two approaches can determine the Higgs boson mass with a similar accuracy for both of the two main production mechanisms of the SM Higgs boson at the LHC, i.e. the gluon-gluon fusion and the weak vector boson fusion. We also notice that the Higgs signal distribution for the gluon-gluon fusion becomes narrower under the M T2 cut, while the corresponding background distribution becomes flatter, indicating that one might be able to reduce the systematic uncertainties of mass measurement with an appropriate M T2 cut.
118706139
MOTIONS OF HARD X-RAY SOURCES DURING AN ASYMMETRIC ERUPTION
Filament eruptions and hard X-ray (HXR) source motions are commonly observed in solar flares, which provide critical information on the coronal magnetic reconnection. This Letter reports an event on 2005 January 15, in which we found an asymmetric filament eruption and a subsequent coronal mass ejection together with complicated motions of HXR sources during the GOES-class X2.6 flare. The HXR sources initially converge to the magnetic polarity inversion line (PIL), and then move in directions either parallel or perpendicular to the PIL depending on the local field configuration. We distinguish the evolution of the HXR source motion in four phases and associate each of them with distinct regions of coronal magnetic fields as reconstructed using a nonlinear force-free field extrapolation. It is found that the magnetic reconnection proceeds along the PIL toward the regions where the overlying field decreases with height more rapidly. It is also found that not only the perpendicular but the parallel motion of the HXR sources correlates well with the HXR light curve. These results are discussed in favor of the torus instability as an important factor in the eruptive process.