Decoupling of the general scalar field mode and the solution space for Bianchi type I and V cosmologies coupled to perfect fluid sources

The scalar field degree of freedom in Einstein's plus Matter field equations is decoupled for Bianchi type I and V general cosmological models. The source, apart from the minimally coupled scalar field with arbitrary potential V(Phi), is provided by a perfect fluid obeying a general equation of state p =p(rho). The resulting ODE is, by an appropriate choice of final time gauge affiliated to the scalar field, reduced to 1st order, and then the system is completely integrated for arbitrary choices of the potential and the equation of state.Comment: latex2e source file,14 pages, no figures; (v3): minor corrections, to appear in J. Math. Phy

The Conformal Sector of F-theory GUTs

D3-brane probes of exceptional Yukawa points in F-theory GUTs are natural hidden sectors for particle phenomenology. We find that coupling the probe to the MSSM yields a new class of N = 1 conformal fixed points with computable infrared R-charges. Quite surprisingly, we find that the MSSM only weakly mixes with the strongly coupled sector in the sense that the MSSM fields pick up small exactly computable anomalous dimensions. Additionally, we find that although the states of the probe sector transform as complete GUT multiplets, their coupling to Standard Model fields leads to a calculable threshold correction to the running of the visible sector gauge couplings which improves precision unification. We also briefly consider scenarios in which SUSY is broken in the hidden sector. This leads to a gauge mediated spectrum for the gauginos and first two superpartner generations, with additional contributions to the third generation superpartners and Higgs sector.Comment: v2: 51 pages, 2 figures, remark added, typos correcte

The Lopsidedness of Present-Day Galaxies: Results from the Sloan Digital Sky Survey

Large-scale asymmetries in the stellar mass distribution in galaxies are believed to trace non-equilibrium situations in the luminous and/or dark matter component. These may arise in the aftermath of events like mergers, accretion, and tidal interactions. These events are key in the evolution of galaxies. In this paper we quantify the large-scale lopsidedness of light distributions in 25155 galaxies at z < 0.06 from the Sloan Digital Sky Survey Data Release 4 using the m = 1 azimuthal Fourier mode. We show that the lopsided distribution of light is primarily due to a corresponding lopsidedness in the stellar mass distribution. Observational effects, such as seeing, Poisson noise, and inclination, introduce only small errors in lopsidedness for the majority of this sample. We find that lopsidedness correlates strongly with other basic galaxy structural parameters: galaxies with low concentration, stellar mass, and stellar surface mass density tend to be lopsided, while galaxies with high concentration, mass, and density are not. We find that the strongest and most fundamental relationship between lopsidedness and the other structural parameters is with the surface mass density. We also find, in agreement with previous studies, that lopsidedness tends to increase with radius. Both these results may be understood as a consequence of several factors. The outer regions of galaxies and low-density galaxies are more susceptible to tidal perturbations, and they also have longer dynamical times (so lopsidedness will last longer). They are also more likely to be affected by any underlying asymmetries in the dark matter halo.Comment: 42 pages, 13 figures, 3 tables, accepted to Ap

Thermodynamics of R-charged Black Holes in AdS(5) From Effective Strings

It is well known that the thermodynamics of certain near-extremal black holes in asymptotically flat space can be lifted to an effective string description created from the intersection of D-branes. In this paper we present evidence that the semiclassical thermodynamics of near-extremal R-charged black holes in AdS(5)xS(5) is described in a similar manner by effective strings created from the intersection of giant gravitons on the S(5). We also present a free fermion description of the supersymmetric limit of the one-charge black hole, and we give a crude catalog of the microstates of the two and three-charge black holes in terms of operators in the dual conformal field theory.Comment: v2: references and typos corrected, 24 pages, latex2

The Higgs as a Probe of Supersymmetric Extra Sectors

We present a general method for calculating the leading contributions to h -> gg and h -> gamma gamma in models where the Higgs weakly mixes with a nearly supersymmetric extra sector. Such mixing terms can play an important role in raising the Higgs mass relative to the value expected in the MSSM. Our method applies even when the extra sector is strongly coupled, and moreover does not require a microscopic Lagrangian description. Using constraints from holomorphy we fix the leading parametric form of the contributions to these Higgs processes, including the Higgs mixing angle dependence, up to an overall coefficient. Moreover, when the Higgs is the sole source of mass for a superconformal sector, we show that even this coefficient is often calculable. For appropriate mixing angles, the contribution of the extra states to h -> gg and h -> gamma gamma can vanish. We also discuss how current experimental limits already lead to non-trivial constraints on such models. Finally, we provide examples of extra sectors which satisfy the requirements necessary to use the holomorphic approximation.Comment: v4: 34 pages, 2 figures, typo corrected and clarification adde

Non-simply-laced Lie algebras via F theory strings

In order to describe the appearance in F theory of the non--simply--laced Lie algebras, we use the representation of symmetry enhancements by means of string junctions. After an introduction to the techniques used to describe symmetry enhancement, that is algebraic geometry, BPS states analysis and string junctions, we concentrate on the latter. We give an explicit description of the folding of D_{2n} to B_n of the folding of E_6 to F_4 and that of D_4 to G_2 in terms of junctions and Jordan strings. We also discuss the case of C_n, but we are unable in this case to provide a string interpretation.Comment: 24 pages, 3 figure

X-ray absorption and rapid variability of the dwarf Seyfert nucleus of NGC4395

We report the detection of an absorbed central X-ray source and its strong, rapid variability in NGC4395, the least luminous Seyfert nucleus known. The X-ray source exhibits a number of flares with factors of 3-4 flux changes during a half day ASCA observation. Such X-ray variability is in constrast to the behaviour of other low luminosity active galaxies. It provides further support for an accreting black hole model rather than an extreme stellar process in accounting for the nuclear activity of NGC4395. The soft X-ray emission below 3 keV is strongly attenuated by absorption. The energy spectrum in this absorption band shows a dramatic change in response to the variation in continuum luminosity. A variable warm absorber appears to be an explanation for the spectral change. The absorption-corrected 2-10 keV luminosity is 4e39 erg/s for a source distance of 2.6 Mpc, and at 1 keV is one order of magnitude above previous ROSAT estimates. Our X-ray results infer the nuclear source of NGC4395 to be a scaled-down version of higher luminosity Seyfert nuclei, with an intermediate mass (10^4-10^5 Msun) black hole, unlike the nearby low luminosity active galaxies in which underfed massive black holes are suspected to reside.Comment: 12 pages, accepted for publication in MNRA

Meta-Stable Brane Configurations of Triple Product Gauge Groups

From an N=1 supersymmetric electric gauge theory with the gauge group SU(N_c) x SU(N_c') x SU(N_c'') with fundamentals for each gauge group and the bifundamentals, we apply Seiberg dual to each gauge group and obtain the N=1 supersymmetric dual magnetic gauge theories with dual matters including the additional gauge singlets. By analyzing the F-term equations of the dual magnetic superpotentials, we describe the intersecting brane configurations of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of this gauge theory. We apply also to the case for N=1 supersymmetric electric gauge theory with the gauge group Sp(N_c) x SO(2N_c') x Sp(N_c'') with flavors for each gauge group and the bifundamentals. Finally, we describe the meta-stable brane configurations of multiple product gauge groups.Comment: 80pp, 10 figures; shorten the draft and to appear in IJMP