From Fake Supergravity to Superstars

The fake supergravity method is applied to 5-dimensional asymptotically AdS spacetimes containing gravity coupled to a real scalar and an abelian gauge field. The motivation is to obtain bulk solutions with R x S^3 symmetry in order to explore the AdS/CFT correspondence when the boundary gauge theory is on R x S^3. A fake supergravity action, invariant under local supersymmetry through linear order in fermion fields, is obtained. The gauge field makes things more restrictive than in previous applications of fake supergravity which allowed quite general scalar potentials. Here the superpotential must take the form W(\phi) ~ exp(-k\phi) + c exp(2\phi/(3k)), and the only freedom is the choice of the constant k. The fermion transformation rules of fake supergravity lead to fake Killing spinor equations. From their integrability conditions, we obtain first order differential equations which we solve analytically to find singular electrically charged solutions of the Lagrangian field equations. A Schwarzschild mass term can be added to produce a horizon which shields the singularity. The solutions, which include "superstars", turn out to be known in the literature. We compute their holographic parameters.Comment: 42 pages, 3 figure

Anti-de Sitter Black Holes in Gauged N=8 Supergravity

We present new anti-de Sitter black hole solutions of gauged N=8, SO(8) supergravity, which is the massless sector of the AdS_4\times S^7 vacuum of M-theory. By focusing on the U(1)^4 Cartan subgroup, we find non-extremal 1, 2, 3 and 4 charge solutions. In the extremal limit, they may preserve up to 1/2, 1/4, 1/8 and 1/8 of the supersymmetry, respectively. In the limit of vanishing SO(8) coupling constant, the solutions reduce to the familiar black holes of the M_4\times T^7 vacuum, but have very different interpretation since there are no winding states on S^7 and no U-duality. In contrast to the T^7 compactification, moreover, we find no static multi-center solutions. Also in contrast, the S^7 fields appear "already dualized" so that the 4 charges may be all electric or all magnetic rather than 2 electric and 2 magnetic. Curiously, however, the magnetic solutions preserve no supersymmetries. We conjecture that a subset of the extreme electric black holes preserving 1/2 the supersymmetry may be identified with the S^7 Kaluza-Klein spectrum, with the non-abelian SO(8) quantum numbers provided by the fermionic zero modes.Comment: 18 pages, Latex, minor notation improvements and references adde

The Local Velocity Anomaly

There is a velocity discontinuity at about 7 Mpc between the galaxies of the Local Sheet that are moving together with low internal velocity dispersion and the adjacent structures. The Local Sheet bounds the Local Void. The Local Sheet is determined to have a peculiar velocity of 260 km/s away from the center of the void. In order for this large velocity to be generated by an absence of gravity, the Local Void must be at least 45 Mpc in diameter and be very empty.Comment: Invited review, "Galaxies in the Local Volume", Sydney, 8-13 July, 2007. eds. B. Koribalski & H. Jerjen, Astrophys. & Space Sci. Proceed. 10 pages with 7 figure

Spin dynamics simulations of the magnetic dynamics of RbMnF3_3 and direct comparison with experiment

Spin-dynamics techniques have been used to perform large-scale simulations of the dynamic behavior of the classical Heisenberg antiferromagnet in simple cubic lattices with linear sizes $L\leq 60$. This system is widely recognized as an appropriate model for the magnetic properties of RbMnF$_3$. Time-evolutions of spin configurations were determined numerically from coupled equations of motion for individual spins using a new algorithm implemented by Krech {\it etal}, which is based on fourth-order Suzuki-Trotter decompositions of exponential operators. The dynamic structure factor was calculated from the space- and time-displaced spin-spin correlation function. The crossover from hydrodynamic to critical behavior of the dispersion curve and spin-wave half-width was studied as the temperature was increased towards the critical temperature. The dynamic critical exponent was estimated to be $z=(1.43\pm 0.03)$, which is slightly lower than the dynamic scaling prediction, but in good agreement with a recent experimental value. Direct, quantitative comparisons of both the dispersion curve and the lineshapes obtained from our simulations with very recent experimental results for RbMnF$_3$ are presented.Comment: 30 pages, RevTex, 9 figures, to appear in PR

Moving toward earlier treatment of multiple sclerosis: Findings from a decade of clinical trials and implications for clinical practice.

The first clinical presentation of multiple sclerosis (MS) is usually a single episode of typical symptoms and signs and is designated a "first clinical demyelinating event" (FCDE) or a "clinically isolated syndrome". Patients with an FCDE who show 'silent' magnetic resonance imaging lesions are at high risk of further clinical events and therefore of meeting the criteria for the diagnosis of clinically definite MS (CDMS). Here we review five Phase III trials, in which treatment with the following disease-modifying drugs (DMDs) was initiated at this early stage: interferon beta (ETOMS, CHAMPS, BENEFIT, and REFLEX) and glatiramer acetate (PreCISe). Differences in the design of the trials and their patient inclusion criteria limit comparisons. However, the proportion of placebo-treated patients who developed CDMS within 2 years was 38–45% across studies, and this rate was significantly reduced by DMD treatment. Conversion t

Non-critical holography and four-dimensional CFT's with fundamentals

We find non-critical string backgrounds in five and eight dimensions, holographically related to four-dimensional conformal field theories with N=0 and N=1 supersymmetries. In the five-dimensional case we find an AdS_5 background metric for a string model related to non-supersymmetric, conformal QCD with large number of colors and flavors and discuss the conjectured existence of a conformal window from the point of view of our solution. In the eight-dimensional string theory, we build a family of solutions of the form AdS_5 x \tilde{S}^3 with \tilde{S}^3 a squashed three-sphere. For a special value of the ratio N_f/N_c, the background can be interpreted as the supersymmetric near-horizon limit of a system of color and flavor branes on R^{1,3} times a known four-dimensional generalization of the cigar. The N=1 dual theory with fundamental matter should have an IR fixed point only for a fixed ratio N_f/N_c. General features of the string/gauge theory correspondence for theories with fundamental flavors are also addressed.Comment: 38 pages, 3 figures; JHEP class. Minor corrections, references adde

D3-branes on the Coulomb branch and instantons

The relative coefficients of higher derivative interactions of the IIB effective action of the form C^4, (D F_5)^4, F_5^8, ... (where C is the Weyl tensor and F_5 is the five-form field strength) are motivated by supersymmetry arguments. It is shown that the classical supergravity solution for N parallel D3-branes is unaltered by this combination of terms. The non-vanishing of \zeroC^2 in this background (where \zero C is the background value of the Weyl tensor) leads to effective O(1/alpha') interactions, such as C^2 and Lambda^8 (where Lambda is the dilatino). These contain D-instanton contributions in addition to tree and one-loop terms. The near horizon limit of the N D3-brane system describes a multi-AdS_5xS^5 geometry that is dual to \calN=4 SU(N) Yang-Mills theory spontaneously broken to S(U(M_1)x...xU(M_r)). Here, the N D3-branes are grouped into r coincident bunches with M_r in each group, with M_r/N = m_r fixed as N goes to infinity. The boundary correlation function of eight Lambda's is constructed explicitly. The second part of the paper considers effects of a constrained instanton in this large-N Yang-Mills theory by an extension of the analysis of Dorey, Hollowood and Khoze of the one-instanton measure at finite N. This makes precise the correspondence with the supergravity D-instanton measure at leading order in the 1/N expansion. However, the duality between instanton-induced correlation functions in Yang-Mills theory and the dual supergravity is somewhat obscured by complications relating to the structure of constrained instantons.Comment: 30 pages, JHEP style. Typos corrected and minor clarifications adde

Gauge-gravity correspondence in de Sitter braneworld

We study the braneworld solutions based on a solvable model of 5d gauged supergravity with two scalars of conformal dimension three, which correspond to bilinear operators of fermions in the dual $\mathcal{N}=4$ super Yang-Mills theory on the boundary. An accelerating braneworld solution is obtained when both scalars are taken as the form of deformations of the super Yang-Mills theory and the bulk supersymmetry is broken. This solution is smoothly connected to the Poincare invariant brane in the limit of vanishing cosmological constant. The stability of this brane-solution and the correspondence to the gauge theory are addressed.Comment: 16 pages, 1 figur

Gravitational Duality in MacDowell-Mansouri Gauge Theory

Strong-weak duality invariance can only be defined for particular sectors of supersymmetric Yang-Mills theories. Nevertheless, for full non-Abelian non-supersymmetric theories, dual theories with inverted couplings, have been found. We show that an analogous procedure allows to find the dual action to the gauge theory of gravity constructed by the MacDowell-Mansouri model plus the superposition of a $\Theta$ term.Comment: 9 pages, LaTeX, no figure