119282193
Expanding universe as a classical solution in the Lorentzian matrix model for nonperturbative superstring theory
Recently we have shown by Monte Carlo simulation that expanding (3+1)-dimensional universe appears dynamically from a Lorentzian matrix model for type IIB superstring theory in (9+1)-dimensions. The mechanism for the spontaneous breaking of rotational symmetry relies crucially on the noncommutative nature of the space. Here we study the classical equations of motion as a complementary approach. In particular, we find a unique class of SO(3) symmetric solutions, which exhibits the time-dependence compatible with the expanding universe. The space-space noncommutativity is exactly zero, whereas the space-time noncommutativity becomes significant only towards the end of the expansion. We interpret the Monte Carlo results and the classical solution as describing the behavior of the model at earlier time and at later time, respectively.
119097342
Torsion as a dynamic degree of freedom of quantum gravity
The gauge approach to gravity based on the local Lorentz group with a general independent affine connection A?cd is developed. We consider SO(1, 3) gauge theory with a Lagrangian quadratic in curvature as a simple model of quantum gravity. The torsion is proposed to represent a dynamic degree of freedom of quantum gravity at scales above the Planckian energy. The Einstein?Hilbert theory is induced as an effective theory due to quantum corrections of torsion via generating a stable gravito-magnetic condensate. We conjecture that torsion possesses an intrinsic quantum nature and can be confined.
118275742
Supersymmetry non-renormalization theorem from a computer and the AdS/CFT correspondence
We perform Monte Carlo calculation of correlation functions in 4d N=4 super Yang-Mills theory on R*S^3 in the planar limit. In order to circumvent the well-known problem of lattice SUSY, we adopt the idea of a novel large-N reduction, which reduces the calculation to that of corresponding correlation functions in the plane-wave matrix model or the BMN matrix model. This model is a 1d gauge theory with 16 supersymmetries, which can be simulated in a manner similar to the recent studies of the D0-brane system. We study two-point and three-point functions of chiral primary operators at various coupling constant, and find that they agree with the free theory results up to overall constant factors. The ratio of the overall factors for two-point and three-point functions agrees with the prediction of the AdS/CFT correspondence.
119232936
Existence of a critical point in the phase diagram of the ideal relativistic neutral Bose gas
We explore the phase transitions of the ideal relativistic neutral Bose gas confined in a cubic box, without assuming the thermodynamic limit nor continuous approximation. While the corresponding non-relativistic canonical partition function is essentially a one-variable function depending on a particular combination of temperature and volume, the relativistic canonical partition function is genuinely a two-variable function of them. Based on an exact expression for the canonical partition function, we performed numerical computations for up to 105 particles. We report that if the number of particles is equal to or greater than a critical value, which amounts to 7616, the ideal relativistic neutral Bose gas features a spinodal curve with a critical point. This enables us to depict the phase diagram of the ideal Bose gas. The consequent phase transition is first order below the critical pressure or second order at the critical pressure. The exponents corresponding to the singularities are 1/2 and 2/3, respectively. We also verify the recently observed 'Widom line' in the supercritical region.
14066902
Classification of the BPS states in Bagger-Lambert Theory
We classify, in a group theoretical manner, the BPS configura tions in the multiple M2-brane theory recently proposed by Bagger and Lambert. We present three types of BPS equations preserving various fractions of supersymmetries: in the first type we have const ant fields and the interactions are purely algebraic in nature; in the second type the equations are inv ariant under spatial rotation SO(2), and the fields can be time-dependent; in the third class the equat ions are invariant under boost SO(1;1) and provide the eleven-dimensional generalizations of the Nahm equations. The BPS equations for different number of supersymmetries exhibit the division a lgebra structures: octonion, quarternion or complex.
16412418
Expanding (3+1)-dimensional universe from a lorentzian matrix model for superstring theory in (9+1) dimensions.
We reconsider the matrix model formulation of type IIB superstring theory in (9+1)-dimensional space-time. Unlike the previous works in which the Wick rotation was used to make the model well defined, we regularize the Lorentzian model by introducing infrared cutoffs in both the spatial and temporal directions. Monte Carlo studies reveal that the two cutoffs can be removed in the large-N limit and that the theory thus obtained has no parameters other than one scale parameter. Moreover, we find that three out of nine spatial directions start to expand at some "critical time," after which the space has SO(3) symmetry instead of SO(9).
119519887
Stellar Companions to Stars with Planets
A combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations. High-resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to the diffraction limit of the Keck 10 m or the Lick 3 m, and direct images or AO images are sensitive to a wider field, extending to 10'' or 38'', depending on the camera. One of the binary system—HD 114762—was not previously known to be a spatially resolved multiple system; additional data taken with the combination of Keck adaptive optics and NIRSPEC are used to characterize the new companion. The second binary system—τ Boo—was a known multiple with two conflicting orbital solutions; the current data will help constrain the discrepant estimates of periastron time and separation. Another target—16 Cyg B—was a known common proper motion binary, but the current data resolve a new third component, close to the wide companion 16 Cyg A. Both the HD 114762 and 16 Cyg B systems harbor planets in eccentric orbits, while the τ Boo binary contains an extremely close planet in a tidally circularized orbit. Although the sample is currently small, the proportion of binary systems is comparable to that measured in the field over a similar separation range. Incorporating the null result from another companion search project lowers the overall fraction of planets in binary systems, but the detections in our survey reveal that planets can form in binaries separated by less than 50 AU.
118561263
Extremal solutions of the S3 model and nilpotent orbits of G2(2)
We study extremal black hole solutions of the S3 model (obtained by setting S=T=U in the STU model) using group theoretical methods. Upon dimensional reduction over time, the S3 model exhibits the pseudo-Riemannian coset structure $ {{G} \left/ {{\tilde{K}}} \right.} $ with G = G2(2) and $ \tilde{K} = {\text{S}}{{\text{O}}_0}\left( {2,2} \right) $. We study nilpotent $ \tilde{K} $-orbits of G2(2) corresponding to non-rotating single-center extremal solutions. We find six such distinct $ \tilde{K} $-orbits. Three of these orbits are supersymmetric, one is non-supersymmetric, and two are unphysical. We write general solutions and discuss examples in all four physical orbits. We show that all solutions in supersymmetric orbits when uplifted to five-dimensional minimal supergravity have single-center Gibbons-Hawking space as their four-dimensional Euclidean hyper-Kähler base space. We construct hitherto unknown extremal (supersymmetric as well as non-supersymmetric) pressureless black strings of minimal five-dimensional supergravity and briefly discuss their relation to black rings.
14036761
Dynamics of assisted quintessence
We explore the dynamics of assisted quintessence, where more than one scalar field is present with the same potential. For potentials with tracking solutions, the fields naturally approach the same values — in the context of inflation this leads to the assisted inflation phenomenon where several fields can cooperate to drive a period of inflation though none is able to individually. For exponential potentials, we study the fixed points and their stability confirming results already in the literature, and then carry out a numerical analysis to show how assisted quintessence is realized. For inverse power-law potentials, we find by contrast that there is no assisted behaviour — indeed those are the unique (monotonic) potentials where several fields together behave just as a single field in the same potential. More generally, we provide an algorithm for generating a single-field potential giving equivalent dynamics to multi-field assisted quintessence.
119284349
The BLG theory in light-cone superspace
The light-cone superspace version of the d = 3, N = 8 superconformal theory of Bagger, Lambert and Gustavsson (BLG) is obtained as a solution to constraints imposed by OSp(2, 2|8) superalgebra. The Hamiltonian of the theory is shown to be a quadratic form of the dynamical supersymmetry transformation.
14759979
Reddening Behaviors of Galaxies in the SDSS Photometric System
ABSTRACT. We analyze the behaviors of reddening vectors in the SDSS photometric system for galaxies of different morphologies, ages, and redshifts. As seen in other photometric systems, the dependence of reddening on the spectral energy distribution (SED) and the nonlinearity of reddening are likewise nonnegligible for the SDSS system if extinction is significant (1mag 1 mag ). These behaviors are most significant for the g g filter, which has the largest bandwidthtocentral-wavelength ratio among SDSS filters. The SDSS colors involving adjacent filters show greater SED dependence and nonlinearity. A procedure for calculating the correct amount of extinction from an observed color excess is provided. The relative extinctions between (i.e., the extinction law for) SDSS filters given by Schlegel etal., which were calculated with an older version of filter response functions, would underestimate the amount of extinction in most cases by 5% 5 % to 10% (maximum 20% 20 % ). We recommend A/A5500 A / A 5500 values...