Topics in String Tachyon Dynamics
We review some aspects of string tachyon dynamics with special emphasis on effective actions
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arXiv subjects
Cesar Gomez
Publications and source records attributed to Cesar Gomez.
A Comment on the K-theory Meaning of the Topology of Gauge Fixing
Based on the recently discovered K-theory description of D-branes in string theory a K-theory interpretation of the topology of gauge conditions for four dimensional gauge theories, in particular 't Hooft abelian projection, is presented. The interpretation of the dyon effect in terms of K^{-1} is also discussed. In the context of type IIA strings, D-p branes are also interpreted as gauge fixing singularities.
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Non-critical Non-singular Bosonic Strings, Linear Dilatons and Holography
$AdS_{5}$ with linear dilaton and non vanishing $B$-field is shown to be a solution of the non critical string beta function equations. A non critical $(D=5)$ solution interpolating between flat space-time and $AdS_{5}$, with asymptotic linear dilaton and non vanishing $B$-field is also presented. This solution is free of space-time singularities and has got the string coupling constant everywhere bounded. Both solutions admit holographic interpretation in terms of ${\cal N}=0$ field theories. Closed string tachyon stability is also discussed.
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Dielectric branes and spontaneous symmetry breaking
A stable non-commutative solution with symmetry breaking is presented for a system of Dp-branes in the presence of a RR (p+5)-form.
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On the String Description of Confinement
A non supersymmetric string background, directly derived from the string soft dilaton theorem, is used to compute, in the semiclassical approximation, the expectation value of Wilson loops in static gauge. The resulting potential shares common features with the one obtained through Schwarzschild-anti de Sitter spacetime metrics. In particular a linear confining potential appears naturally.
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Brane World with Bulk Horizons
A brane world in the presence of a bulk black hole is constructed. The brane tension is fine tuned in terms of the black hole mass and cosmological constant. Gravitational perturbations localized on the brane world are discussed.
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Dilatonic Randall-Sundrum Theory and renormalisation group
We extend Randall-Sundrum dynamics to non-conformal metrics corresponding to non-constant dilaton. We study the appareance of space-time naked singularities and the renormalization group evolution of four-dimensional Newton constant.
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A Comment on the Holographic Renormalization Group and the Soft Dilaton Theorem
The equivalence between the holographic renormalization group and the soft dilaton theorem is shown for a class of wrapped metrics solutions of the string beta function equations for the bosonic string.
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T-duality and The Gravitational Description Of Gauge Theories
This is a review of some basic features on the relation between supergravity and pure gauge theories with special emphasis on the relation between T-duality and supersymmetry. Some new results concerning the interplay between T-duality and near horizon geometries are presented
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Ultraviolet and Infrared freedom from string amplitudes
The infinite tension limit of string amplitudes is examined with some care, identifying the part responsible of diamagnetic behaviour as well as a peculiar paramagnetic {\em tachyon magnifying} responsible of asymptotic freedom. The way string theory represents abelian gauge theories is connected with the non-planar reggeon/pomeron amplitude and a nontrivial beta function is found in the low energy limit of a single D-brane.
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The Confining String from the Soft Dilaton Theorem
A candidate for the confining string of gauge theories is constructed via a representation of the ultraviolet divergences of quantum field theory by a closed string dilaton insertion, computed through the soft dilaton theorem. The resulting (critical) confining string is conformally invariant, singles out naturally $d=4$ dimensions, and can not be used to represent theories with Landau poles.
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Geometric Holography, the Renormalization Group and the c-Theorem
In this paper the whole geometrical set-up giving a conformally invariant holographic projection of a diffeomorphism invariant bulk theory is clarified. By studying the renormalization group flow along null geodesic congruences a holographic version of Zamolodchikov's c-theorem is proven.
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Elliptic Singularities, θ-Puzzle and Domain Walls
We study N=1 four dimensional gluodynamics in the context of M-theory compactifications on elliptically fibered Calabi-Yau fourfolds. Gaugino condensates, θ-dependence, Witten index and domain walls are considered for singularities of type $\hat{A}_{n-1}$ and $\hat{D}_{n+4}$. It is shown how the topology of intersections among the irreducible components defining the singular elliptic fiber, determine the entanglement of vacua and the appareance of domain walls.
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On the geometry of soft breaking terms and N=1 superpotentials
We describe, in the context of M-theory on elliptically fibered Calabi-yau fourfolds, the change of variables that allow us to pass from the U(1) invariant elliptic fibration to the one describing the uncompactified four dimensional limit, where the U(1) symmetry is broken. These changes of variables are the analog to the ones used to derive from the Atiyah-Hitchin space the complex structure of the Seiberg-Witten solution for N=2 supersymmetric Yang-Mills. The connection between these changes of variables and the recently introduced rotation of branes is discussed.
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M-Theory, Torons and Confinement
We study the decompactification limit of M-theory superpotentials for N=1 four dimensional supersymmetric gauge theories. These superpotentials can be interpreted as generated by toron configurations. The connection with the confinement picture in the maximal abelian gauge is discussed.
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M and F-Theory Instantons, N=1 Supersymmetry and Fractional Topological Charges
We analize instanton generated superpotentials for three dimensional N=2 supersymmetric gauge theories obtained by compactifying on S^1 N=1 four dimensional theories. In the N_f=1 case, we find that the vacua in the decompactification limit is given by the singular points of the Coulomb branch of the N=2 four dimensional theory (we also consider the massive case). The decompactification limit of the superpotential for pure gauge theories without chiral matter is interpreted in terms of `t Hooft's fractional instanton amplitudes.
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D-Brane Probes and Mirror Symmetry
We study the effect of mirror symmetry for K3 surfaces on D-brane probe physics. The case of elliptically fibered K3 surfaces is considered in detail. In many cases, mirror can transform a singular fiber of Kodaira's type ADE into sets of singular fibers of type I_1 (II) with equal total Euler number, but vanishing contribution to the Picard number of the mirror surface. This provides a geometric model of quantum splitting phenomena. Mirror for three dimensional gauge theories, interchanging Fayet-Iliopoulos and mass terms, is also briefly discussed.
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Electric-Magnetic Duality and Effective Field Theories
Lectures given by C.G. in the Advanced School on Effective Theories (Almuñecar, Granada, 1995) on duality in N=2 supersymmetric Yang-Mills, and the coupling to gravity.
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