S-Duality and the Dyon Spectrum in N=2 Super Yang-Mills Theory

We study the dyon spectrum in $N=2$ Super Yang-Mills theory with gauge group $SU(2)$ coupled to $N_f$ matter multiplets in the fundamental representation. For magnetic charge one and two we determine the spectrum explicitly and show that it is in agreement with the duality predictions of Seiberg and Witten. We briefly discuss the extension to higher charge monopoles for the self-dual $N_f=4$ case and argue that the conjectured spectrum of dyons predicts the existence of certain harmonic spinors on the moduli space of higher charge monopoles.Comment: 32 pages, harvma

Evanescent Black Holes

A renormalizable theory of quantum gravity coupled to a dilaton and conformal matter in two space-time dimensions is analyzed. The theory is shown to be exactly solvable classically. Included among the exact classical solutions are configurations describing the formation of a black hole by collapsing matter. The problem of Hawking radiation and backreaction of the metric is analyzed to leading order in a $1/N$ expansion, where $N$ is the number of matter fields. The results suggest that the collapsing matter radiates away all of its energy before an event horizon has a chance to form, and black holes thereby disappear from the quantum mechanical spectrum. It is argued that the matter asymptotically approaches a zero-energy ``bound state'' which can carry global quantum numbers and that a unitary $S$-matrix including such states should exist.Comment: 14 page

Grief and Avoidant Death Attitudes Combine to Predict the Fading Affect Bias

The fading affect bias (FAB) occurs when unpleasant affect fades faster than pleasant affect. To detect mechanisms that influence the FAB in the context of death, we measured neuroticism, depression, anxiety, negative religious coping, death attitudes, and complicated grief as potential predictors of FAB for unpleasant/death and pleasant events at 2 points in time. The FAB was robust across older and newer events, which supported the mobilization-minimization hypothesis. Unexpectedly, complicated grief positively predicted FAB, and death avoidant attitudes moderated this relation, such that the Initial Event Affect by Grief interaction was only significant at the highest 3 quintiles of death avoidant attitudes. These results were likely due to moderate grief ratings, which were, along with avoidant death attitudes, related to healthy outcomes in past research. These results implicate complicated grief and death avoidant attitudes as resiliency mechanisms that are mobilized during bereavement to minimize its unpleasant effects

N=1 String Duality

We discuss duality between Type IIA string theory, eleven-dimensional supergravity, and heterotic string theory in four spacetime dimensions with $N=1$ supersymmetry. We find theories whose infrared limit is trivial at enhanced symmetry points as well as theories with $N=1$ supersymmetry but the field content of $N=4$ theories which flow to the $N=4$ fixed line in the infrared.Comment: 14 pages, harvma

Black Holes with a Massive Dilaton

The modifications of dilaton black holes which result when the dilaton acquires a mass are investigated. We derive some general constraints on the number of horizons of the black hole and argue that if the product of the black hole charge $Q$ and the dilaton mass $m$ satisfies $Q m < O(1)$ then the black hole has only one horizon. We also argue that for $Q m > O(1)$ there may exist solutions with three horizons and we discuss the causal structure of such solutions. We also investigate the possible structures of extremal solutions and the related problem of two-dimensional dilaton gravity with a massive dilaton.Comment: 36 pages with 5 figures (as uuencoded compressed tar file) (revised version has one major change in bound on mass for extremal solution and minor typos fixed), harvma

Inhomogeneous tachyon condensation

We investigate the spacetime-dependent condensation of the tachyon in effective field theories. Previous work identified singularities in the field which appear in finite time: infinite gradients at the kinks, and (in the eikonal approximation) caustics near local minima. By performing a perturbation analysis, and with numerical simulations, we demonstrate and explain key features of the condensation process: perturbations generically freeze, and minima develop singular second derivatives in finite time (caustics). This last has previously been understood in terms of the eikonal approximation to the dynamics. We show explicitly from the field equations how this approximation emerges, and how the caustics develop, both in the DBI and BSFT effective actions. We also investigate the equation of state parameter of tachyon matter showing that it is small, but generically non-zero. The energy density tends to infinity near field minima with a charateristic profile. A proposal to regulate infinities by modifying the effective action is also studied. We find that although the infinities at the kinks are successfully regularised in the time-dependent case, caustics still present.Comment: 4 figures,19p

Scattering of Macroscopic Heterotic Strings

We show that macroscopic heterotic strings, formulated as strings which wind around a compact direction of finite but macroscopic extent, exhibit non-trivial scattering at low energies. This occurs at order velocity squared and may thus be described as geodesic motion on a moduli space with a non-trivial metric which we construct. Our result is in agreement with a direct calculation of the string scattering amplitude.Comment: 14 pp (harvmac l

The M2-M5 Brane System and a Generalized Nahm's Equation

We propose an equation that describes M2-branes ending on M5-branes, and which generalizes the description of the D1-D3 system via Nahm's equation. The simplest solution to this equation constructs the transverse geometry in terms of a fuzzy three sphere. We show that the solution passes a number of consistency checks including a consistent reduction to the D1-D3 system, a calculation of the energy of the system, matching to the self-dual string solution in the M5-brane world volume, and a study of simple fluctuations about the ground state configuration. We write down certain terms in the effective action of multiple membranes, which includes a sextic scalar coupling.Comment: 19 pages, LaTe

Hairy Black Holes in String Theory

Solutions of bosonic string theory are constructed which correspond to four-dimensional black holes with axionic quantum hair. The basic building blocks are the renormalization group flows of the CP1 model with a theta term and the SU(1,1)/U(1) WZW coset conformal field theory. However the solutions are also found to have negative energy excitations, and are accordingly expected to decay to the vacuum.Comment: 14 pages (References added

Quantum Topologically Massive Gravity in de Sitter Space

We consider three dimensional gravity with a positive cosmological constant and non- zero gravitational Chern-Simons term. This theory has inflating de Sitter solutions and local metric degrees of freedom. The Euclidean signature partition function of the theory is evaluated including both perturbative and non-perturbative corrections. The perturbative one-loop correction is computed using heat kernel techniques. The non- perturbative corrections come from gravitational instantons with non-trivial topology which can be enumerated explicitly. We compute the sum over an infinite class of ge- ometries and show that, unlike the case of pure Einstein gravity, the partition function is finite. This demonstrates that the inclusion of non-trivial local degrees of freedom can render the sum over geometries convergent.Comment: 25 pages, 1 figure; v2: minor correction