Nonabelian Fields in Exact String Solutions

Within the framework of "anomalously gauged" Wess-Zumino-Witten (WZW) models, we construct solutions which include nonabelian fields. Both compact and noncompact groups are discussed. In the case of compact groups, as an example of background containing nonabelian fields, we discuss conformal theory on the $SO(4)/SO(3)$ coset, which is the natural generalization of the 2D monopole theory corresponding to the $SO(3)/SO(2)$ coset. In noncompact case, we consider examples with $SO(2,1)/SO(1,1)$ and $SO(3,2)/SO(3,1)$ cosets.Comment: 15 pages, Late

On Black Hole Thermodynamics of 2-D Type 0A

We present a detailed analysis of the thermodynamics of two dimensional black hole solutions to type 0A with q units of electric and magnetic flux. We compute the free energy and derived quantities such as entropy and mass for an arbitrary non-extremal black hole. The free energy is non-vanishing, in contrast to the case of dilatonic 2-d black holes without electric and magnetic fluxes. The entropy of the extremal black holes is obtained, and we find it to be proportional to q^2, the square of the RR flux. We compare these thermodynamics quantities with those from candidate matrix model duals.Comment: 20pp, v2: references adde

One-loop Effective Action of the Holographic Antisymmetric Wilson Loop

We systematically study the spectrum of excitations and the one-loop determinant of holographic Wilson loop operators in antisymmetric representations of $\mathcal{N}=4$ supersymmetric Yang-Mills theory. Holographically, these operators are described by D5-branes carrying electric flux and wrapping an $S^4 \subset S^5$ in the $AdS_5\times S^5$ bulk background. We derive the dynamics of both bosonic and fermionic excitations for such D5-branes. A particularly important configuration in this class is the D5-brane with $AdS_2\times S^4$ worldvolume and $k$ units of electric flux, which is dual to the circular Wilson loop in the totally antisymmetric representation of rank $k$. For this Wilson loop, we obtain the spectrum, show explicitly that it is supersymmetric and calculate the one-loop effective action using heat kernel techniques.Comment: 42 pages, one tabl

3-branes on resolved conifold

The type IIB supergravity solution describing a collection of regular and fractional D3 branes on the conifold (hep-th/0002159) was recently generalized to the case of the deformed conifold (hep-th/0007191). Here we present another generalization -- when the conifold is replaced by the resolved conifold. This solution can be found in two different ways: (i) by first explicitly constructing the Ricci-flat Kahler metric on resolved conifold and then solving the supergravity equations for the D3-brane ansatz with constant dilaton and (self-dual) 3-form fluxes; (ii) by generalizing the ``conifold'' ansatz of hep-th/0002159 in a natural ``asymmetric'' way so that the 1-d action describing radial evolution still admits a superpotential and then solving the resulting 1-st order system. The superpotentials for the ``resolved'' and ``deformed'' conifold cases turn out to have essentially the same simple structure. The solution in the resolved conifold case has the same asymptotic UV behaviour as in the conifold case, but unlike the deformed conifold case is still singular in the IR. The naked singularity is of repulson type and may have a brane resolution.Comment: 19 pages, latex. v2,v3: misprints correcte

Conformal Sigma Models for a Class of Tp,qT^{p,q} Spaces

We consider a 2-d conformal theory based on (G x G')/ H coset sigma model introduced by Guadagnini, Martellini and Mintchev. It is shown that in the case of {SU(2) x SU(2)}/ U(1) the metric of the corresponding background is of T^{p,q} coset space form (but is not an Einstein one). Similar interpretation is possible for the Lorentzian coset space W_{4,2}= {SL(2,R) x SL(2,R)}/U(1). The resulting 10-d homogeneous space metric on W_{4,2} x T^{p,q} supplemented with 2-form field gives a critical NS-NS superstring background with conformal sigma model interpretation.Comment: 8 pages, late

Low-Temperature Glassy Response of Ultrathin Manganite Films to Electric and Magnetic Fields

The glassy response of thin films of La0.8Ca0.2MnO3 to external magnetic and gated electrostatic fields in a field-effect geometry has been studied at low temperatures. A hierarchical response with irreversible memory effects, non-ergodic time evolution, aging and annealing behavior of the resistance suggest that the dynamics are governed by strain relaxation for both electronic and magnetic perturbations. Cross-coupling of charge, spin, and strain have been exploited to tune the coercivity of an ultrathin manganite film by electrostatic gating.Comment: 4 pages, 5 figure