Decay Rates of Fixed Planes and Closed-string Tachyons on Unstable Orbifolds

We consider closed-string tachyon condensation in the twisted sectors on the C/Z_{2n+1} \times R^{7,1} orbifold. We calculate the localized energy density in the fixed plane on the orbifold at the one-loop level, and we obtain the decay rate per unit volume of the fixed plane to leading order. We show that the decay rate increases monotonically as a function of n.Comment: 19 pages, 2 figures, LaTeX. v2: typos corrected. v3: section 5 is modified, main results unchanged. v4: published version in Prog. Theor. Phy

Dirichlet Boundary Conditions in Generalized Liouville Theory toward a QCD String

We consider bosonic noncritical strings as QCD strings and we present a basic strategy to construct them in the context of Liouville theory. We show that Dirichlet boundary conditions play important roles in generalized Liouville theory. Specifically, they are used to stabilize the classical configuration of strings and also utilized to treat tachyon condensation in our model. We point out that Dirichlet boundary conditions for the Liouville mode maintains Weyl invariance, if an appropriate condition is satisfied, in the background with a (non-linear) dilaton.Comment: 21 pages, Latex. Typos corrected. The final version for Prog.Theor.Phy

Recoiling D-branes

We propose a new method to describe a recoiling D-brane that is elastically scattered by closed strings in the non-relativistic region. We utilize the low-energy effective field theory on the worldvolume of the D-brane, and the velocity of the D-brane is described by the time derivative of the expectation values of the massless scalar fields on the worldvolume. The effects of the closed strings are represented by a source term for the massless fields in this method. The momentum conservation condition between the closed strings and the D-brane is derived up to the relative sign of the momentum of the D-brane.Comment: 23 pages, 1 figure, LaTeX, v2: a reference added, minor change in section 4.2, v3, v4: minor corrections, to appear in Nucl. Phys.

Negative Differential Resistivity from Holography

Negative differential resistivity (NDR) in a (3+1)-dimensional quantum system of strongly correlated charge carriers is theoretically reproduced by using the AdS/CFT correspondence. Our system is microscopically defined, and the analysis does not rely on any phenomenological models of NDR mechanism. The interaction between the heat reservoir and the nonequilibrium charge carriers is also taken into account. The system realizes insulation due to the formation of the neutral bound states of the charge carriers at low temperatures. However, the insulation is broken and the field-induced conductor phase appears by applying the external electric field greater than the critical value. We find that the NDR appears right above the critical electric field in this phase, and the pair creation of the charge carriers is crucial to realize the NDR. The present result suggests a possibility to observe a similar NDR in excitonic insulators or in the strongly interacting quark-gluon plasma, where the insulation originates in the formation of the neutral bound states.Comment: 4 pages, 2 figures;V2 typos corrected, reference added;V3: 12 pages by changing the format; comments, references, figures added, NcNf is modified without changing the main results. 4 figures;V4: published version; V5: nothing changed except for the format,10 page