A Geometry for Non-Geometric String Backgrounds

A geometric string solution has background fields in overlapping coordinate patches related by diffeomorphisms and gauge transformations, while for a non-geometric background this is generalised to allow transition functions involving duality transformations. Non-geometric string backgrounds arise from T-duals and mirrors of flux compactifications, from reductions with duality twists and from asymmetric orbifolds. Strings in ` T-fold' backgrounds with a local $n$-torus fibration and T-duality transition functions in $O(n,n;\Z)$ are formulated in an enlarged space with a $T^{2n}$ fibration which is geometric, with spacetime emerging locally from a choice of a $T^n$ submanifold of each $T^{2n}$ fibre, so that it is a subspace or brane embedded in the enlarged space. T-duality acts by changing to a different $T^n$ subspace of $T^{2n}$. For a geometric background, the local choices of $T^n$ fit together to give a spacetime which is a $T^n$ bundle, while for non-geometric string backgrounds they do not fit together to form a manifold. In such cases spacetime geometry only makes sense locally, and the global structure involves the doubled geometry. For open strings, generalised D-branes wrap a $T^n$ subspace of each $T^{2n}$ fibre and the physical D-brane is the part of the part of the physical space lying in the generalised D-brane subspace.Comment: 28 Pages. Minor change

Quantum Mechanics of the Doubled Torus

We investigate the quantum mechanics of the doubled torus system, introduced by Hull [1] to describe T-folds in a more geometric way. Classically, this system consists of a world-sheet Lagrangian together with some constraints, which reduce the number of degrees of freedom to the correct physical number. We consider this system from the point of view of constrained Hamiltonian dynamics. In this case the constraints are second class, and we can quantize on the constrained surface using Dirac brackets. We perform the quantization for a simple T-fold background and compare to results for the conventional non-doubled torus system. Finally, we formulate a consistent supersymmetric version of the doubled torus system, including supersymmetric constraints.Comment: 31 pages, 1 figure; v2: references added, minor corrections to final sectio

New Gauged N=8, D=4 Supergravities

New gaugings of four dimensional N=8 supergravity are constructed, including one which has a Minkowski space vacuum that preserves N=2 supersymmetry and in which the gauge group is broken to $SU(3)xU(1)^2$. Previous gaugings used the form of the ungauged action which is invariant under a rigid $SL(8,R)$ symmetry and promoted a 28-dimensional subgroup ($SO(8),SO(p,8-p)$ or the non-semi-simple contraction $CSO(p,q,8-p-q)$) to a local gauge group. Here, a dual form of the ungauged action is used which is invariant under $SU^*(8)$ instead of $SL(8,R)$ and new theories are obtained by gauging 28-dimensional subgroups of $SU^*(8)$. The gauge groups are non-semi-simple and are different real forms of the $CSO(2p,8-2p)$ groups, denoted $CSO^*(2p,8-2p)$, and the new theories have a rigid SU(2) symmetry. The five dimensional gauged N=8 supergravities are dimensionally reduced to D=4. The $D=5,SO(p,6-p)$ gauge theories reduce, after a duality transformation, to the $D=4,CSO(p,6-p,2)$ gauging while the $SO^*(6)$ gauge theory reduces to the $D=4, CSO^*(6,2)$ gauge theory. The new theories are related to the old ones via an analytic continuation. The non-semi-simple gaugings can be dualised to forms with different gauge groups.Comment: 33 pages. Reference adde

On the construction of variant supergravities in D=11, D=10

We construct with a geometric procedure the supersymmetry transformation laws and Lagrangian for all the ``variant'' D=11 and D=10 Type IIA supergravities. We identify into our classification the D=11 and D=10 Type IIA ``variant'' theories first introduced by Hull performing T-duality transformation on both spacelike and timelike circles. We find in addition a set of D=10 Type IIA ``variant'' supergravities that can not be obtained trivially from eleven dimensions compactifying on a circle.Comment: 21 pages, Late

Generalised Geometry for M-Theory

Generalised geometry studies structures on a d-dimensional manifold with a metric and 2-form gauge field on which there is a natural action of the group SO(d,d). This is generalised to d-dimensional manifolds with a metric and 3-form gauge field on which there is a natural action of the group $E_{d}$. This provides a framework for the discussion of M-theory solutions with flux. A different generalisation is to d-dimensional manifolds with a metric, 2-form gauge field and a set of p-forms for $p$ either odd or even on which there is a natural action of the group $E_{d+1}$. This is useful for type IIA or IIB string solutions with flux. Further generalisations give extended tangent bundles and extended spin bundles relevant for non-geometric backgrounds. Special structures that arise for supersymmetric backgrounds are discussed.Comment: 31 page

Antioxidant and antihypertensive activities of rice bran peptides

Protein isolates and peptide fractions from food sources (cereal grains), have been shown to exert bioactive properties including antiobesity, anticancer, antiangiogenic, etc. One such food source is rice bran, which is an underutilized co-product of rough rice milling. It contains 90% of the nutrients and nutraceuticals of value to health, including high quality protein. The high quality protein is a potential source to generate peptides that can reduce hypertension and oxidative stress, both being important risk factors for cardiovascular diseases. The objective of this study was to extract peptide hydrolysates from heat stabilized defatted rice bran by enzymatic hydrolysis, evaluate the hydrolysates for gastrointestinal (GI) resistance, fractionate the GI-resistant hydrolysates by ultrafiltration to obtain \u3e50 and 10-50 kDa fractions, and determine antihypertensive and antioxidant activities in the fractions. For antihypertension activity, angiotension-1 converting enzyme (ACE) assay, and for antioxidant activity, the 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) assay was conducted. We report that the ACE-I inhibition activity values for the unfractionated and unhydrolyzed (control), and fractions of \u3e50 kDa, and 10-50 kDa were 6% (control), 78%, and 55%, respectively, clearly denoting antihypertensive activity for the peptide fractions. When tested for antioxidant activity, the \u3e50 kDa fraction decreased from an initial DPPH of 95.48 to 78.99 mg/g, while the 10-50 kDa fraction decreased from an initial 110.35 to 76.53 mg/g, depicting reduction of radical-induced oxidant stress. The results demonstrated that the high molecular sized peptide hydrolysate fractions (\u3e50 and 10-50 kDa) from rice bran bear antihypertensive and antioxidant properties and could possibly find a place as a health beneficial nutraceutical ingredient in food applications

Duality Symmetric Strings, Dilatons and O(d,d) Effective Actions

We calculate the background field equations for the T-duality symmetric string building on previous work by including the effect of the Dilaton up to two-loops. Inclusion of the Dilaton allows us to obtain the full beta functionals of the duality symmetric sigma model. We are able to interpret the result in terms of a dimensionally reduced O(d,d) invariant target space effective action.Comment: 15 pages, latex; v2 reference added, typos fixe

D=6, N=2, F(4)-Supergravity with supersymmetric de Sitter Background

We show that there exists a supersymmetric de Sitter background for the D=6, N=2, F(4) supergravity preserving the compact R-symmetry and gauging with respect to the conventional Anti de Sitter version of the theory. We construct the gauged matter coupled F(4) de Sitter supergravity explicitly and show that it contains ghosts in the vector sector.Comment: 19 pages, Late