Table of contents

We discuss a solution of the equations of motion of five-dimensional gauged type IIB supergravity that describes confining SU(N) gauge theories at large N and large 't Hooft parameter. We prove confinement by computing the Wilson loop, and we show that our solution is generic, independent of most of the details of the theory. In particular, the Einstein-frame metric near its singularity, and the condensates of scalar, composite operators are universal. Also universal is the discreteness of the glueball mass spectrum and the existence of a mass gap. The metric is also identical to a generically confining solution recently found in type 0B theory.

In the microcanonical ensemble for string theory on AdS_m × Sⁿ, there is a phase transition between a black hole solution extended over the Sⁿ and a solution localized on the Sⁿ if theAdS_m has the topology ² × S^m−2. The phase transition will not appear if the AdS_m has the topology ² × T^m−2, that is, when the AdS_m × Sⁿ geometry is regarded as arising from the near-horizon limit of a black m−2 brane. In this paper, we argue that when the black branes are rotating, the localization phase transition will occur between some rotating branes and corresponding Kerr black holes when the angular momentum reaches its critical value.

We consider Type 0B D3-branes placed at conical singularities and analyze in detail the conifold singularity. We study the non supersymmetric gauge theories on their worldvolume and their conjectured dual gravity descriptions. In the ultraviolet the solutions exhibit a logarithmic running of the gauge coupling. In the infrared we find confining solutions and IR fixed points.

The experimental data on atmospheric and solar neutrinos are used to test the framework of non-anomalous Abelian horizontal gauge symmetries with only three light active neutrinos. We assume that the hierarchy in mass-squared splittings is not accidental and that the small breaking parameters are not considerably larger than 0.2. We find that the small angle MSW solution of the solar neutrino problem can only be accommodated if the ν_μ−ν_τ mass hierarchy depends on the charges of at least three sterile neutrinos. The large angle MSW solution can be accommodated in simpler models if ν_e and ν_μ form a pseudo-Dirac neutrino, but it is difficult to induce large enough deviation from maximal mixing. The vacuum oscillation solution can be accommodated rather simply. We conclude that it is possible to accommodate the neutrino parameters in the framework of Abelian horizontal symmetries, but it seems that these parameters by themselves will not provide convincing evidence for this framework.

It is pointed out that a natural introduction of quintessence is an axion with an almost massless quark. With an appropriate gauge or discrete symmetry, one can obtain the quintessence potential height of order (0.003 eV)⁴. Even though the QCD axion with almost massless up quark is a possibility, we stress the almost massless quark in the hidden sector together with the QCD axion toward the quintessence.

Energy bounds are derived for planar and compactified M2-branes in a hyper-Kähler background. These bounds are saturated, respectively, by lump and Q-kink solitons, which are shown to preserve half the worldvolume supersymmetry. The Q-kinks have a dual IIB interpretation as strings that migrate between fivebranes.

We propose a method to investigate the conservation of brane charges at the intersection of two or more branes using the Thom classes of their normal bundles. In particular we find a relation between the charge of the branes involved in the configuration and the charge of the defects on the branes due to the intersection. We also explore the applications of our method for various brane intersections in type II strings and M-theory.

The GS superstring on AdS₅ × S⁵ has a nonlinearly realized, spontaneously broken SU(2,2|4) symmetry. Here we introduce a two-dimensional model in which the unbroken SU(2,2|4) symmetry is linearly realized. The basic variables are supertwistors, which transform in the fundamental representation of this supergroup. The quantization of this supertwistor model leads to the complete oscillator construction of the unitary irreducible representations of the centrally extended SU(2,2|4). They include the states of d = 4 SYM theory, massless and KK states of AdS₅ supergravity, and the descendants on AdS₅ of the standard massive string states, which form intermediate and long massive supermultiplets. We present examples of long massive supermultiplets and discuss possible states of solitonic and (p,q) strings.

In this letter, we introduce a general theory for the construction of particle physics theories, with three families and realistic gauge groups, within the context of heterotic M-theory. This is achieved using semi-stable holomorphic gauge bundles over elliptically fibered Calabi-Yau three-folds. Construction of realistic theories is facilitated by the appearance of non-perturbative five-branes in the vacuum. The complete moduli space of these five-branes is computed and their worldvolume gauge theory discussed. In the context of holomorphic gauge bundles, it is shown how grand unified gauge groups can be spontaneously broken to the gauge group of the standard model. These ideas are illustrated in an explicit SU(5) three-family example.

According to one of Maldacena's dualities, type IIB string theory on AdS₃ × S³ × K3 is equivalent to a certainN = (4,4) superconformal field theory. In this note we compute the elliptic genus of the boundary theory in the supergravity approximation. A finite quantity is obtained once we introduce a particular exclusion principle. In the regime where the supergravity approximation is reliable, we find exact agreement with the elliptic genus of a sigma model with target space K3^N/S_N.

We calculate within the MSSM the one--loop Yukawa coupling corrections to the processes e⁺e⁻→0_ibar−_j, _ibar−_j, _ibar−_j in order of Yukawa coupling squared. These corrections are due to the exchange of charginos, neutralinos, charged and neutral Higgs bosons, and charged and neutral Higgs ghosts. We give the complete analytical formulae. We also perform a detailed numerical analysis of the Yukawa coupling corrections, including also the SUSY-QCD corrections. It turns out that for stop and sbottom production the Yukawa coupling corrections are typically ∼ ±10% of the tree--level cross section. For stau production they are about ±5%.

We study the asymptotic limits of the heterotic string theories compactified on tori. We find a bilinear form uniquely determined by dualities which becomes Lorentzian in the case of one spacetime dimension. For the case of the SO(32) theory, the limiting descriptions include SO(32) heterotic strings, type I, type IA and other T-duals, M-theory on K3, type IIA theory on K3 and type IIB theory on K3 and possibly new limits not understood yet.

We continue the construction of non-trivial vacua for gauge theories on the 3--torus. Application of constructions based on twist in SU(N) with N > 2 produce more extra vacua in theories with exceptional groups. We calculate the relevant unbroken subgroups, and their contribution to the Witten index. We show that the extra vacua we find in the exceptional groups are sufficient to solve the Witten index problem for these groups.

We discuss a recently proposed scenario where the sparticle masses are purely mediated by gravity through the superconformal anomaly. This scenario elegantly evades the supersymmetric flavor problem since soft masses, like the anomaly, are not directly sensitive to ultraviolet physics. However, its minimal incarnation fails by predicting tachyonic sleptons. We study the conditions for decoupling of heavy threshold effects and how these conditions are evaded. We use these results to build a realistic class of models where the non-decoupling effects of ultra-heavy vectorlike matter fields eliminate the tachyons. These models have a flavor invariant superspectrum similar to that of gauge mediated models. They, however, differ in several aspects: the gaugino masses are not unified, the colored sparticles are not much heavier than the others, the μ problem is less severe and the gravitino mass is well above the weak scale, m_3/2≳10 TeV. We also show that in models where anR-symmetry can be gauged, the associated D-term gives rise to soft terms that are similarly insensitive to the ultraviolet.

We consider in this paper a Left-Right symmetric gauge model in which a global lepton-number-like symmetry is introduced and broken spontaneously at a scale ω that could be as low as 10⁴ GeV or so. The corresponding physical Nambu-Goldstone boson, which we call majoron and denote J, can have tree-level flavour-violating couplings to the charged fermions, leading to sizeable majoron-emitting lepton-flavour-violating weak decays. We consider explicitly a leptonic variant of the model and show that the branching ratios for μ→e+J, τ→e+J and τ→μ+J decays can be large enough to fall within the sensitivities of future μ and τ factories. On the other hand the left-right gauge symmetry breaking scale may be as low as few TeV.

We derive the complete (curvature)² terms of effective D-brane actions, for arbitrary ambient geometries and world-volume embeddings, at lowest order (disk-level) in the string-loop expansion. These terms reproduce the o(α'²) corrections to string scattering amplitudes, and are consistent with duality conjectures. In the particular case of the D3-brane with trivial normal bundle, considerations of SL(2,) invariance lead to a complete sum of D-instanton corrections for both the parity-conserving and the parity-violating parts of the effective action. These corrections are required for the cancellation of the modular anomalies of massless modes, and are consistent with the absence of chiral anomalies in the intersection domain of pairs of D-branes. We also show that the parity-conserving part of the non-perturbative R² action follows from a one-loop quantum calculation in the six-dimensional world-volume of the M5-brane compactified on a two-torus.

The low energy effective action describing the standard Kaluza-Klein reduction of heterotic string theory on a d-torus possesses a manifest O(d,d+16) symmetry. We consider generalized Scherk-Schwarz reductions of the heterotic string to construct massive gauged supergravities. We show that the resulting action can still be written in a manifestly O(d,d+16) invariant form, however, the U-duality transformations also act on the mass parameters. The latter play the dual role of defining the scalar potential and the nonabelian structure constants. We conjecture that just as for the standard reduction, a subgroup of this symmetry corresponds to an exact duality symmetry of the heterotic string theory.

We analyse the canonical structure of AdS₃ gravity in terms of the coadjoint orbits of the Virasoro group. There is one subset of orbits, associated to BTZ black hole solutions, that can be described by a pair of chiral free fields with a background charge. There is also a second subset of orbits, associated to point-particle solutions, that are described by two pairs of chiral free fields obeying a constraint. All these orbits admit Kähler quantization and generate a Hilbert space which, despite of having Δ₀(bar-Δ₀) = 0, does not provide the right degeneracy to account for the Bekenstein-Hawking entropy due to the breakdown of modular invariance. Therefore, additional degrees of freedom, reestablishing modular invariance, are necessarily required to properly account for the black hole entropy.

We consider theories characterized by a set of Ward operators which do not form a closed algebra. We impose the Slavnov-Taylor identity built out of the Ward operators and we derive the acceptable breaking of the algebra and the general form of the classical action. The 1PI generating functional is expressed in terms of the known quantities characterizing the theory and of a nontrivial integrability condition. As a nontrivial application of our formalism, we discuss the N = 4 supersymmetric nonlinear sigma model.

In the note a simple calculation of one loop threshold corrections for the SO(32) heterotic string is performed. In particular the compactification on T² with a Wilson line breaking the gauge group to SO(16) × SO(16) is considered. Using heterotic type I duality, these corrections can be related to quantities appearing in the quantum mechanics of type I' D0 particles.

We study = (2,2) supersymmetric abelian gauge theories in two dimensions. The exact BPS spectrum of these models is shown to coincide with the spectrum of massive hypermultiplets of certain = 2 supersymmetric gauge theories in four dimensions. A special case of these results involves a surprising connection between four-dimensional = 2 SQCD with N colours andN_f>N flavours at the root of the baryonic Higgs branch and the supersymmetric CP^2N−N_f−1 σ-model in two dimensions. This correspondence implies a new prediction for the strong-coupling spectrum of the four-dimensional theory.

We discuss the gauge theory mechanisms which are responsible for the causal structure of the dual supergravity. For D-brane probes we show that the light cone structure and Killing horizons of supergravity emerge dynamically. They are associated with the appearance of new light degrees of freedom in the gauge theory, which we explicitly identify. This provides a picture of physics at the horizon of a black hole as seen by a D-brane probe.

As a novel application of string junctions, we construct stable non-BPS states on a 3-brane probe in the 7-brane background associated with N = 2 SU(2) Super-Yang-Mills theory. These states introduce a second curve of marginal stability, across which some of them decay. Moduli space is therefore divided into four regions, each containing a different stable particle spectrum.

This paper lays groundwork for the detailed study of the non-trivial renormalization group flow connecting supersymmetric fixed points in four dimensions using string theory on AdS spaces. Specifically, we consider D3-branes placed at singularities of Calabi-Yau threefolds which generalize the conifold singularity and have an ADE classification. The = 1 superconformal theories dictating their low-energy dynamics are infrared fixed points arising from deforming the corresponding ADE = 2 superconformal field theories by mass terms for adjoint chiral fields. We probe the geometry with a single D3-brane and discuss the near-horizon supergravity solution for a large number N of coincidentD3-branes.

We study the potential between a string and an anti-string source in M5-theory by using the AdS/CFT duality conjecture. We find that the next to leading order corrections in a saddle point approximation renormalize the classical result.

We propose a construction of non-trivial vacua for Yang-Mills theories on the 3-torus. Although we consider theories with periodic boundary conditions, twisted boundary conditions play an essential auxiliary role in our construction. In this article we will limit ourselves to the simplest case, based on twist in SU(2) subgroups. These reproduce the recently constructed new vacua for SO(N) and G₂ theories on the 3-torus. We show how to embed the results in the other exceptional groups F₄ and E_6,7,8 and how to compute the relevant unbroken subgroups. In a subsequent article we will generalise to SU(N > 2) subgroups. The number of vacua found this way exactly matches the number predicted by the calculation of the Witten index in the infinite volume.