Branes with Background Fields in Boundary State Formalism

Interaction of branes in presence of internal gauge fields is considered by using the boundary state formalism. This approach enables us to consider the problems that are not easily accessible to the canonical approach via open strings. The effects of compactification of some of the dimensions on tori are also discussed. Also we study the massless state contribution on this interaction.Comment: 12 pp. No figure

Heavy quark potential in the instanton liquid model

We study the heavy quark potential in the instanton liquid model by carefully measuring Wilson loops out to a distance of order 3$fm$. A random instanton ensemble with a fixed radius $\rho$ = 1/3$fm$ generates a potential $V(R)$ growing very slowly at large $R$. In contrast, a more realistic size distribution growing as $\rho^6$ at small $\rho$ and decaying as $\rho^{-5}$ at large $\rho$, leads to a potential which grows linearly with $R$. The string tension, however, is only about 1/10 of the phenomenological value.Comment: LATTICE98(confine

Gauge Fields and Space-Time

In this article I attempt to collect some ideas,opinions and formulae which may be useful in solving the problem of gauge/ string / space-time correspondence This includes the validity of D-brane representation, counting of gauge-invariant words, relations between the null states and the Yang-Mills equations and the discussion of the strong coupling limit of the string sigma model. The article is based on the talk given at the "Odyssey 2001" conference.Comment: 20 page

Mixed Branes Interaction in Compact Spacetime

We present a general description of two mixed branes interactions. For this we consider two mixed branes with dimensions p_1 and p_2, in external field B_{\mu\nu} and arbitrary gauge fields A^1_{\alpha_1} and A^2_{\alpha_2} on the world volume of them, in spacetime in which some of its directions are compactified on circles with different radii. Some examples are considered to clear these general interactions. Finally contribution of the massless states on the interactions is extracted. Closed string with mixed boundary conditions and boundary state formalism, provide useful tools for calculation of these interactions.Comment: 22 pages, to appear in Nucl. Phys.

Born-Infeld strings between D-branes

We examine the solutions of world-volume action for a D3-brane being put near other D3-brane which is replaced by the background configuration of bulk space. It is shown that the BPS solutions are not affected by the D3-brane background, and they are interpreted as dyonic strings connecting two branes. On the contrary, the non-BPS configurations are largely influenced by the background D-brane, and we find that the solutions with pure electric charge cannot connect two branes. These solutions are corresponding to the bound state of brane and anti-brane which has been found by Callan and MaldacenaComment: 14 pages, 8 figure

Anomaly induced effective actions in even dimensions and reliability of s-wave approximation

The reduction of 4d matter-gravity theory to $S_2$, $H_2$ or $R_2$ leads to effective 2d dilatonic gravity with dilaton coupled matter. Spinors give the exceptional example of the theory which is conformally invariant in 4d as well as in 2d, after reduction. We find 4d and 2d conformal anomaly induced effective action (EA) for Majorana spinor. It is expected for some time that s-wave EA (i.e. the one for dilaton coupled 2d matter) is some (s-wave) approximation to 4d EA. We compare such 2d and 4d spinor EAs on the same gravitational background and argue that s-wave EA indeed qualitatively corresponds to no higher derivatives approximation for 4d EA.Comment: LaTeX file, 12 pages, the discussion of the Hawking radiation is adde

Function generator eliminates necessity of series summation

Diode generator using four building-block circuits produces complex waveforms without the necessity of series summation. This highly specialized method of producing complex waveforms requires less power than present methods and uses simpler circuitry

Fundamental Strings as Black Bodies

We show that the decay spectrum of massive excitations in perturbative string theories is thermal when averaged over the (many) initial degenerate states. We first compute the inclusive photon spectrum for open strings at the tree level showing that a black body spectrum with the Hagedorn temperature emerges in the averaging. A similar calculation for a massive closed string state with winding and Kaluza-Klein charges shows that the emitted graviton spectrum is thermal with a "grey-body" factor, which approaches one near extremality. These results uncover a simple physical meaning of the Hagedorn temperature and provide an explicit microscopic derivation of the black body spectrum from a unitary $S$ matrix.Comment: some changes in the Discussion section and in the reference list. 11 pages, Late

A grid-based infrastructure for distributed retrieval

In large-scale distributed retrieval, challenges of latency, heterogeneity, and dynamicity emphasise the importance of infrastructural support in reducing the development costs of state-of-the-art solutions. We present a service-based infrastructure for distributed retrieval which blends middleware facilities and a design framework to ‘lift’ the resource sharing approach and the computational services of a European Grid platform into the domain of e-Science applications. In this paper, we give an overview of the DILIGENT Search Framework and illustrate its exploitation in the field of Earth Science

Charged Black Holes in Two-Dimensional String Theory

We discuss two dimensional string theories containing gauge fields introduced either via coupling to open strings, in which case we get a Born-Infeld type action, or via heterotic compactification. The solutions to the modified background field equations are charged black holes which exhibit interesting space-time geometries. We also compute their masses and charges.Comment: 39 page