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

Comment on Counting Black Hole Microstates Using String Dualities

We discuss a previous attempt at a microscopic counting of the entropy of asymptotically flat non-extremal black-holes. This method used string dualities to relate 4 and 5 dimensional black holes to the BTZ black hole. We show how the dualities can be justified in a certain limit, equivalent to a near horizon limit, but the resulting spacetime is no longer asymptotically flat.Comment: 10 pages, harvmac. v(2) typo correcte

Stringy Probe Particle and Force Balance

We directly derive the classical equation of motion, which governs the centre of mass of a test string, from the string action. In a certain case, the equation is basically same as one derived by Papapetrou, Dixon and Wald for a test extended body. We also discuss the force balance using a stringy probe particle for an exact spinning multi-soliton solution of Einstein-Maxwell-Dilaton-Axion theory. It is well known that the force balance condition yields the saturation of the Bogomol'nyi type bound in the lowest order. In the present formulation the gyromagnetic ratio of the stringy probe particle is automatically determined to be $g=2$ which is the same value as the background soliton. As a result we can confirm the force balance via the gravitational spin-spin interaction.Comment: 8 pages, references added, comments added, Phys. Rev. D accepte

Absorption of Fixed scalars and the D-brane Approach to Black Holes

We calculate the emission and absorption rates of fixed scalars by the near-extremal five-dimensional black holes that have recently been modeled using intersecting D-branes. We find agreement between the semi-classical and D-brane computations. At low energies the fixed scalar absorption cross-section is smaller than for ordinary scalars and depends on other properties of the black hole than just the horizon area. In the D-brane description, fixed scalar absorption is suppressed because these scalars must split into at least four, rather than two, open strings running along the D-brane. Consequently, this comparison provides a more sensitive test of the effective string picture of the D-brane bound state than does the cross-section for ordinary scalars. In particular, it allows us to read off the value of the effective string tension. That value is precisely what is needed to reproduce the near-extremal 5-brane entropy.Comment: 33 pages, harvmac, version to appear in Nucl. Phys.

Solitonic Strings and BPS Saturated Dyonic Black Holes

We consider a six-dimensional solitonic string solution described by a conformal chiral null model with non-trivial $N=4$ superconformal transverse part. It can be interpreted as a five-dimensional dyonic solitonic string wound around a compact fifth dimension. The conformal model is regular with the short-distance (`throat') region equivalent to a WZW theory. At distances larger than the compactification scale the solitonic string reduces to a dyonic static spherically-symmetric black hole of toroidally compactified heterotic string. The new four-dimensional solution is parameterised by five charges, saturates the Bogomol'nyi bound and has nontrivial dilaton-axion field and moduli fields of two-torus. When acted by combined T- and S-duality transformations it serves as a generating solution for all the static spherically-symmetric BPS-saturated configurations of the low-energy heterotic string theory compactified on six-torus. Solutions with regular horizons have the global space-time structure of extreme Reissner-Nordstrom black holes with the non-zero thermodynamic entropy which depends only on conserved (quantised) charge vectors. The independence of the thermodynamic entropy on moduli and axion-dilaton couplings strongly suggests that it should have a microscopic interpretation as counting degeneracy of underlying string configurations. This interpretation is supported by arguments based on the corresponding six-dimensional conformal field theory. The expression for the level of the WZW theory describing the throat region implies a renormalisation of the string tension by a product of magnetic charges, thus relating the entropy and the number of oscillations of the solitonic string in compact directions.Comment: 27 Pages, uses RevTeX (solution for the axion field corrected, erratum to appear in Phys. Rev. D

On (multi-)center branes and exact string vacua

Multicenter supergravity solutions corresponding to Higgs phases of supersymmetric Yang-Mills theories are considered. For NS5 branes we identify three cases where there is a description in terms of exact conformal field theories. Other supergravity solutions, such as D3-branes with angular momentum, are understood as special limits of multicenter ones. Within our context we also consider 4-dim gravitational multi-instantons.Comment: 9 pages, latex; To be published in the proceedings of the Quantum Aspects of Gauge Theories, Supersymmetry and Unification, Corfu, Greece, 20-26 September 199

Thermodynamics of doubly charged CGHS model and D1-D5-KK black holes of IIB supergravity

We study the doubly charged Callan-Giddings-Harvey-Strominger (CGHS) model, which has black hole solutions that were found to be U-dual to the D1-D5-KK black holes of the IIB supergravity. We derive the action of the model via a spontaneous compactification on S^3 of the IIB supergravity on S^1*T^4 and obtain the general static solutions including black holes corresponding to certain non-asymptotically flat black holes in the IIB supergravity. Thermodynamics of them is established by computing the entropy, temperature, chemical potentials, and mass in the two-dimensional setup, and the first law of thermodynamics is explicitly verified. The entropy is in precise agreement with that of the D1-D5-KK black holes, and the mass turns out to be consistent with the infinite Lorentz boost along the M theory circle that is a part of the aforementioned U-dual chain.Comment: 21 pages, Revte

Wavy Strings: Black or Bright?

Recent developments in string theory have brought forth a considerable interest in time-dependent hair on extended objects. This novel new hair is typically characterized by a wave profile along the horizon and angular momentum quantum numbers $l,m$ in the transverse space. In this work, we present an extensive treatment of such oscillating black objects, focusing on their geometric properties. We first give a theorem of purely geometric nature, stating that such wavy hair cannot be detected by any scalar invariant built out of the curvature and/or matter fields. However, we show that the tidal forces detected by an infalling observer diverge at the `horizon' of a black string superposed with a vibration in any mode with $l \ge 1$. The same argument applied to longitudinal ($l=0$) waves detects only finite tidal forces. We also provide an example with a manifestly smooth metric, proving that at least a certain class of these longitudinal waves have regular horizons.Comment: 45 pages, latex, no figure

Boundary states as exact solutions of (vacuum) closed string field theory

We show that the boundary states are idempotent B*B=B with respect to the star product of HIKKO type closed string field theory. Variations around the boundary state correctly reproduce the open string spectrum with the gauge symmetry. We explicitly demonstrate it for the tachyonic and massless vector modes. The idempotency relation may be regarded as the equation of motion of closed string field theory at a possible vacuum.Comment: 30 pages, 2 figures, v3:regularization improve

General Static Solutions of 2-dimensional Einstein-Dilaton-Maxwell-Scalar Theories

General static solutions of effectively 2-dimensional Einstein-Dilaton-Maxwell-Scalar theories are obtained. Our model action includes a class of 2-d dilaton gravity theories coupled with a $U(1)$ gauge field and a massless scalar field. Therefore it also describes the spherically symmetric reduction of $d$-dimensional Einstein-Scalar-Maxwell theories. The properties of the analytic solutions are briefly discussed.Comment: 16 pages, Latex fil