119208046
Composite magnetic dark matter and the 130 GeV line
We propose an economical model to explain the apparent 130 GeV gamma ray peak, found in the Fermi/LAT data, in terms of dark matter annihilation through a dipole moment interaction. The annihilating dark matter particles represent a subdominant component, with mass density 7-17% of the total DM density; and they only annihilate into gamma gamma, gamma Z, and ZZ, through a magnetic (or electric) dipole moment. Annihilation into other standard model particles is suppressed, due to a mass splitting in the magnetic dipole case, or to p-wave scattering in the electric dipole case. In either case, the observed signal requires a dipole moment of strength mu ~ 2/TeV. We argue that composite models are the preferred means of generating such a large dipole moment, and that the magnetic case is more natural than the electric one. We present a simple model involving a scalar and fermionic techniquark of a confining SU(2) gauge symmetry. We point out some generic challenges for getting such a model to work. The new physics leading to a sufficiently large dipole moment is below the TeV scale, indicating that the magnetic moment is not a valid effective operator for LHC physics, and that production of the strongly interacting constituents, followed by techni-hadronization, is a more likely signature than monophoton events. In particular, 4-photon events from the decays of bound state pairs are predicted.
119023526
The phantom menaced: Constraints on low-energy effective ghosts
It has been suggested that a scalar field with negative kinetic energy, or ``ghost,'' could be the source of the observed late-time cosmological acceleration. Naively, such theories should be ruled out by the catastrophic quantum instability of the vacuum. We derive phenomenological bounds on the Lorentz-violating ultraviolet cutoff $\ensuremath{\Lambda}$ which must apply to low-energy effective theories of ghosts, in order to keep the instability at unobservable levels. Assuming only that ghosts interact at least gravitationally, we show that $\ensuremath{\Lambda}\ensuremath{\lesssim}3\mathrm{MeV}$ for consistency with the cosmic gamma ray background. We also show that theories of ghosts with a Lorentz-conserving cutoff are completely excluded.
118416779
Next-to-leading order thermal photon production in a weakly coupled quark-gluon plasma
A bstractWe compute the next-to-leading order O(g) correction to the thermal photon production rate in a QCD plasma. The NLO contributions can be expressed in terms of gauge invariant condensates on the light cone, which are amenable to novel sum rules and Euclidean techniques. We expect these technologies to be generalizable to other NLO calculations. For the phenomenologically interesting value of αs = 0.3, the NLO correction represents a 20% increase and has a functional form similar to the LO result.
18843095
Classical sphaleron rate on fine lattices
We measure the sphaleron rate for hot, classical Yang-Mills theory on the lattice, in order to study its dependence on lattice spacing. By using a topological definition of Chern-Simons number and going to extremely fine lattices [up to $\ensuremath{\beta}=32,$ or lattice spacing ${a=1/(8g}^{2}T)]$ we demonstrate nontrivial scaling. The topological susceptibility, converted to physical units, falls with lattice spacing on fine lattices in a way which is consistent with linear dependence on a (the Arnold-Son-Yaffe scaling relation) and is difficult to reconcile with a nonzero continuum limit. We also explain some unusual behavior of the rate in small volumes, reported by Ambj\o{}rn and Krasnitz.
10799212
Classical field dynamics of the electroweak phase transition
We investigate the thermodynamics and dynamics of the electroweak phase transition by modeling the infrared physics with classical Yang-Mills Higgs theory. We discuss the accuracy of this approach and conclude that, for quantities whose determination is dominated by the infrared, the classical method should be correct up to parametrically suppressed [i.e., O({alpha})] corrections. For a Higgs self-coupling which at the tree level corresponds to m{sub H}{approx_equal}50 GeV, we determine the jump in the order parameter to be {delta}{phi}=1.5gT, the surface tension to be {sigma}=0.07g{sup 4}T{sup 3}, and the friction coefficient on the moving bubble wall due to infrared bosons to be {eta}{equivalent_to}P/v{sub w}=0.03{plus_minus}0.004g{sup 6}T{sup 4}. We also investigate the response of the Chern-Simons number to a spatially uniform chemical potential and find that it falls off a short distance inside the bubble wall, both in equilibrium and below the equilibrium temperature. {copyright} {ital 1997} {ital The American Physical Society}
119279378
Bjorken flow, plasma instabilities, and thermalization
A bstractAt asymptotically high energies, thermalization in heavy ion collisions can be described via weak-coupling QCD. We present a complete treatment of how thermalization proceeds, at the parametric weak-coupling level. We show that plasma instabilities dominate the dynamics, from immediately after the collision until well after the plasma becomes nearly in equilibrium. Initially they drive the system close to isotropy, but Bjorken expansion and increasing diluteness makes the system again become more anisotropic. At time $ \tau \sim {\alpha^{{\frac{{ - 12}}{5}}}}Q_s^{{ - 1}} $ the dynamics become dominated by a nearly-thermal bath; and at time $ \tau \sim {\alpha^{{\frac{{ - 5}}{2}}}}Q_s^{{ - 1}} $ the bath comes to dominate the energy density, completing thermalization. After this time there is a nearly isotropic and thermal Quark-Gluon Plasma.
3095614
K-theory and Ramond-Ramond charge
We discuss the relation between the Ramond-Ramond charges of D-branes and the topology of Chan-Paton vector bundles. We show that a topologically nontrivial normal bundle induces RR charge and that the result fits in perfectly with the proposal that D-brane charge is the topology of the Chan-Paton bundle, regarded as an element of K-theory.
15744838
Instabilities in heterotic M-theory induced by open membrane instantons
Abstract We study the effective low energy supergravity of the strongly coupled heterotic string compactified on a Calabi–Yau 3-fold with generic E 8 × E 8 gauge bundle. We focus on the effective potential for the chiral scalars. The effective superpotential can be studied using the dual 11-dimensional M-theory background involving insertions of M5-branes along an interval. In such backgrounds, in some regions of moduli space, the leading nonperturbative contributions are due to open membrane instantons. These instantons lead to both attractive and repulsive forces between the 5-branes and the orientifold “M9-branes”, depending on the region of moduli space. The resulting dynamics on moduli space include a strong coupling dual to the Dine–Seiberg instability, in which the interval grows. We discuss conditions under which the 5-branes are attracted to the wall and comment on the relevance of these results to the study of chirality-changing phase transitions in heterotic M-theory.
3949031
Superconformal Invariance and the Geography¶of Four-Manifolds
Abstract:The correlation functions of supersymmetric gauge theories on a four-manifold X can sometimes be expressed in terms of topological invariants of X. We show how the existence of superconformal fixed points in the gauge theory can provide nontrivial information about four-manifold topology. In particular, in the example of gauge group SU(2) with one doublet hypermultiplet, we derive a theorem relating classical topological invariants such as the Euler character and signature to sum rules for Seiberg–Witten invariants. A short account of this paper can be found in [1].
16606536
Classification of Abelian spin Chern-Simons theories
We derive a simple classification of quantum spin Chern-Simons theories with gauge group T=U(1)^N. While the classical Chern-Simons theories are classified by an integral lattice the quantum theories are classified differently. Two quantum theories are equivalent if they have the same invariants on 3-manifolds with spin structure, or equivalently if they lead to equivalent projective representations of the modular group. We prove the quantum theory is completely determined by three invariants which can be constructed from the data in the classical action. We comment on implications for the classification of fractional quantum Hall fluids.
11977234
Ample D4-D2-D0 Decay
We study the wall-crossing behavior of the index of BPS states for D4-D2-D0 brane systems on a Calabi-Yau 3-fold at large radius and point out that not only is the ``BPS index at large radius'' chamber-dependent, but that the changes in the index can be large in the sense that they dominate single-centered black hole entropy. We discuss implications for the weak coupling OSV conjecture. We also analyze the near horizon limit of multicentered solutions, introduced in arXiv:0802.2257, for these particular configurations and comment on a general criterion, conjectured in arXiv:0802.2257, which identifies those multicentered solutions whose near horizon limit corresponds to a geometry with a single asymptotic AdS_3 x S^2 boundary.