Type IIA Orientifold Limit of M-Theory on Compact Joyce 8-Manifold of Spin(7)-Holonomy

We show that M-theory compactified on a compact Joyce 8-manifold of $Spin(7)$-holonomy, which yields an effective theory in $D = 3$ with $\N$ = 1 supersymmetry, admits at some special points in it moduli space a description in terms of type IIA theory on an orientifold of compact Joyce 7-manifold of $G_2$-holonomy. We find the evidence in favour of this duality by computing the massless spectra on both M-thory side and type IIA side. For the latter, we compute the massless spectra by going to the orbifold limit of the Joyce 7-manifold.Comment: 26 pages, 2 eps figures, Latex file, two references and one footnote added, corrected some typo

Glueballs of Super Yang-Mills from Wrapped Branes

In this paper we study qualitative features of glueballs in N=1 SYM for models of wrapped branes in IIA and IIB backgrounds. The scalar mode, 0++ is found to be a mixture of the dilaton and the internal part of the metric. We carry out the numerical study of the IIB background. The potential found exhibits a mass gap and produces a discrete spectrum without any cut-off. We propose a regularization procedure needed to make these states normalizable.Comment: 22 pages plus a appendixes, 2 figure

Transport modeling of nonlinearly adsorbing solutes in physically heterogeneous pore networks

The purpose of this study is to upscale nonlinearly reactive transport from the pore scale to a heterogeneous porous medium with the aid of a sufficiently large three-dimensional pore network model. We consider a porous medium that is chemically homogeneous (sorption reactivity is constant in space) but physically heterogeneous, as it has a spatially variable pore size. Our numerical experiments aim to assess whether traveling wave (TW) behavior develops and to assess how large a network is required to be to allow our conclusions. This study revealed that for this purpose the network should include more than a million pore units and that this size varies with the degree of heterogeneity. This assertion is based on temporal changes of the moments of a migrating front of nonlinearly adsorbing solute. In networks of equal sized pores, TW behavior occurs, and concentration distributions can be predicted by an analytical solution. For increasing physical heterogeneity the balance between the dispersive and adsorptive forces remains absent because the second central moment continues to grow as a function of time. The growth rate of this moment is a function of pore-scale heterogeneit

Supersymmetric Boost on Intersecting D-branes

We study the effect of the Born-Infeld electric field on the supersymmetric configuration of various composite D-branes. We show that the generic values of the electric field do not affect the supersymmetry but, as it approaches $1/2\pi\alpha'$ keeping the magnetic field finite, various combinations of the magnetic fields allow up to 8 supersymmetries. We also explore the unbroken supersymmetries for two intersecting D-strings which are in uniform or relative motion. For a finite uniform Lorentz boost, 16 supersymmetries are guaranteed only when they are parallel. For an infinite one, 8 supersymmetries are preserved only when both the D-strings are oriented to the forward or backward direction of the boost. Under a finite relative boost, 8 supersymmetries are preserved only when the intersecting angle is less than $\pi/2$ and the intersecting point moves at the speed of light. As for an infinite relative boost, 8 supersymmetries are preserved regardless of the values of the intersecting angle.Comment: 27 pages using REVTeX4, 7 figure

Chern-Simons Matrix Models and Unoriented Strings

For matrix models with measure on the Lie algebra of SO/Sp, the sub-leading free energy is given by F_{1}(S)=\pm{1/4}\frac{\del F_{0}(S)}{\del S}. Motivated by the fact that this relationship does not hold for Chern-Simons theory on S^{3}, we calculate the sub-leading free energy in the matrix model for this theory, which is a Gaussian matrix model with Haar measure on the group SO/Sp. We derive a quantum loop equation for this matrix model and then find that F_{1} is an integral of the leading order resolvent over the spectral curve. We explicitly calculate this integral for quadratic potential and find agreement with previous studies of SO/Sp Chern-Simons theory.Comment: 28 pages, 2 figures V2: re-organised for clarity, results unchange

D-branes on AdS flux compactifications

We study D-branes in N=1 flux compactifications to AdS_4. We derive their supersymmetry conditions and express them in terms of background generalized calibrations. Basically because AdS has a boundary, the analysis of stability is more subtle and qualitatively different from the usual case of Minkowski compactifications. For instance, stable D-branes filling AdS_4 may wrap trivial internal cycles. Our analysis gives a geometric realization of the four-dimensional field theory approach of Freedman and collaborators. Furthermore, the one-to-one correspondence between the supersymmetry conditions of the background and the existence of generalized calibrations for D-branes is clarified and extended to any supersymmetric flux background that admits a time-like Killing vector and for which all fields are time-independent with respect to the associated time. As explicit examples, we discuss supersymmetric D-branes on IIA nearly Kaehler AdS_4 flux compactifications.Comment: 43 pages, 2 pictures, 1 table; v2: added references, color to figure and corrected typo in (6.21b

Branes on Generalized Calibrated Submanifolds

We extend previous results on generalized calibrations to describe supersymmetric branes in supergravity backgrounds with diverse fields turned on, and provide several new classes of examples. As an important application, we show that supersymmetric D-branes in compactifications with field strength fluxes, and on SU(3)-structure spaces, wrap generalized calibrated submanifolds, defined by simple conditions in terms of the underlying globally defined, but non-closed, 2- and 3-forms. We provide examples where the geometric moduli of D-branes (for instance D7-branes in 3-form flux configurations) are lifted by the generalized calibration condition. In addition, we describe supersymmetric D6-branes on generalized calibrated 3-submanifolds of half-flat manifolds, which provide the mirror of B-type D-branes in IIB CY compactifications with 3-form fluxes. Supersymmetric sets of such D-branes carrying no homology charges are mirror to supersymmetric sets of D-branes which are homologically non-trivial, but trivial in K-theory. As an additional application, we describe models with chiral gauge sectors, realized in terms of generalized calibrated brane box configurations of NS- and D5-branes, which are supersymmetric but carry no charges, so that no orientifold planes are required in the compactification.Comment: 40 pages, 3 figures, references adde

From D-Dbar Pairs to Branes in Motion

We investigate various supersymmetric brane intersections. Motivated by the recent results on supertubes, we investigate general constraints in which parallel brane-antibrane configurations are supersymmetric. Dual descriptions of these configurations involve systems of branes in relative motion. In particular, we find new supersymmetric configurations which are not related to a static brane intersection by a boost. In these new configurations, the intersection point moves at the speed of light. These systems provide interesting time dependent backgrounds for open strings.Comment: 28+1 pages, 8 figures, uses JHEP3.cl

Yukawa couplings in intersecting D-brane models

We compute the Yukawa couplings among chiral fields in toroidal Type II compactifications with wrapping D6-branes intersecting at angles. Those models can yield realistic standard model spectrum living at the intersections. The Yukawa couplings depend both on the Kahler and open string moduli but not on the complex structure. They arise from worldsheet instanton corrections and are found to be given by products of complex Jacobi theta functions with characteristics. The Yukawa couplings for a particular intersecting brane configuration yielding the chiral spectrum of the MSSM are computed as an example. We also show how our methods can be extended to compute Yukawa couplings on certain classes of elliptically fibered CY manifolds which are mirror to complex cones over del Pezzo surfaces. We find that the Yukawa couplings in intersecting D6-brane models have a mathematical interpretation in the context of homological mirror symmetry. In particular, the computation of such Yukawa couplings is related to the construction of Fukaya's category in a generic symplectic manifold.Comment: 47 pages, using JHEP3.cls, 11 figures. Typos and other minor corrections. References adde

Thermostatistics of deformed bosons and fermions

Based on the q-deformed oscillator algebra, we study the behavior of the mean occupation number and its analogies with intermediate statistics and we obtain an expression in terms of an infinite continued fraction, thus clarifying successive approximations. In this framework, we study the thermostatistics of q-deformed bosons and fermions and show that thermodynamics can be built on the formalism of q-calculus. The entire structure of thermodynamics is preserved if ordinary derivatives are replaced by the use of an appropriate Jackson derivative and q-integral. Moreover, we derive the most important thermodynamic functions and we study the q-boson and q-fermion ideal gas in the thermodynamic limit.Comment: 14 pages, 2 figure