The occurrence of a bounce in FRW cosmology requires modifications of generalrelativity. An example of such a modification is the recently proposedHorava-Lifshitz theory of gravity, which includes a ``dark radiation'' termwith a negative coefficient in the analog of the Friedmann

The pure Skyrme-Faddeev-Niemi model (i.e., without quadratic kinetic term)with a potential is considered on the spacetime S^3 x R. For one-vacuumpotentials two types of exact Hopf solitons are obtained. Depending on thevalue of the Hopf index, we find compact or

We study the fluid-like dynamics of eigenvalues of the Wilson operator in thecontext of the order-disorder (Durhuus-Olesen) transition in large $N_c$Yang-Mills theory. We link the universal behavior at the closure of the gapfound by Narayanan and Neuberger to the phenomenon

It is well-known that chiral symmetry breaking ($\chi$SB) in QCD with$N_{f}=2$ light quark flavours can be described by orthogonal groups as $O(4)\to O(3)$, due to local isomorphisms. Here we discuss the question how specificthis property is. We consider generalised forms

In the present work, we search static charged black hole solutions toHo\v{r}ava-Lifshitz gravity with or without projectability condition. Weconsider the most general form of action which electromagnetic field coupleswith Ho\v{r}ava-Lifshitz gravity. With the projectability condition, we finddS-Reissner-Nordstrom black hole solution

We perform a perturbative (near-critical) analysis of the stability of anasymptotically Schroedinger Reissner-Nordstrom black hole with respect togeneration of charged scalar hair. We find that apart from the expectedinstability at low temperatures typical of holographic models ofsuperconductivity, in the presence

In this paper, which is a revised version of the author's PhD thesis, weanalyze two different applications of string theory. In the first part, wefocus on four dimensional compactifications of Type II string theoriespreserving N=1 supersymmetry, in presence of intersecting

We revisit an old idea that gravity can be unified with Yang-Mills theory byenlarging the gauge group of gravity formulated as gauge theory. Our startingpoint is an action that describes a generally covariant gauge theory for agroup G. The Minkowski

The Grassmann structure of the critical XXZ spin chain is studied in thelimit to conformal field theory. A new description of Virasoro Verma modules isproposed in terms of Zamolodchikov's integrals of motion and two families offermionic creation operators. The exact

In this paper, we calculate the next to the leading order Casimir energy forreal massive and massless scalar fields within $\lambda\phi^{4}$ theory,confined between two parallel plates with the Dirichlet boundary condition intwo spatial dimensions. Our results are finite in both

Light-cone gauge NSR string theory in noncritical dimensions shouldcorrespond to a string theory with a nonstandard longitudinal part.Supersymmetrizing the bosonic case [], we formulate asuperconformal worldsheet theory for the longitudinal variables X^{\pm},\psi^{\pm}. We show that with the transverse variables and

We study a scalar field with kinetic term coupled to itself and to thecurvature, as a source of dark energy, and analyze the role of this newcoupling in the accelerated expansion at large times. In the case of scalarfield dominance,

Principal axis transformation is performed for a Lagrangian with a U(1)-SU(2)mixing term, that can cause a SU(2) deconfining transition.

We construct a simple holographic QCD model to study nuclear matter tostrange matter transition. The interaction of dense medium and hadrons is takencare of by imposing the force balancing condition for stable D4/D6/D6configuration. By considering the intermediate and light flavor

This Chapter outlines the replica approach in Random Matrix Theory. Bothfermionic and bosonic versions of the replica limit are introduced and itstrickery is discussed. A brief overview of early heuristic treatments ofzero-dimensional replica field theories is given to advocate an

Chiral gauge theories can be defined in four-dimensional Anti de Sitterspace, but AdS boundary conditions explicitly break the chiral symmetry in aspecific, well defined manner, which in turns results in an anomalous Wardidentity. When the 4D theory admits a dual

In the context of bubble universes produced by a first-order phase transitionwith large nucleation rates compared to the inverse dynamical time scale of theparent bubble, we extend the usual analysis to non-vacuum backgrounds. Inparticular, we provide semi-analytic and numerical results

For the integrable higher-spin XXX and XXZ spin chains we presentmultiple-integral representations for the correlation function of an arbitraryproduct of Hermitian elementary matrices in the massless ground state. We givea formula expressing it by a single term of multiple integrals.

We explore supersymmetry breaking in the light of a rich fixed-pointstructure of two-dimensional supersymmetric Wess-Zumino models with onesupercharge using the functional renormalization group (RG). We relate thedynamical breaking of supersymmetry to an RG relevant control parameter of thesuperpotential which is

In this paper we study the entropy perturbations in N-flation by using the$\d\ma{N}$ formalism. We calculate the entropy corrections to the powerspectrum of the overall curvature perturbation $P_{\z}$. We obtain an analyticform of the transfer coefficient $T^2_{\ma{R}\ma{S}}$, which describes thecorrelation