Chern-Simons Field Theories with Non-semisimple Gauge Group of Symmetry

Subject of this work is a class of Chern-Simons field theories with non-semisimple gauge group, which may well be considered as the most straightforward generalization of an Abelian Chern-Simons field theory. As a matter of fact these theories, which are characterized by a non-semisimple group of gauge symmetry, have cubic interactions like those of non-abelian Chern-Simons field theories, but are free from radiative corrections. Moreover, at the tree level in the perturbative expansion,there are only two connected tree diagrams, corresponding to the propagator and to the three vertex originating from the cubic interaction terms. For such theories it is derived here a set of BRST invariant observables, which lead to metric independent amplitudes. The vacuum expectation values of these observables can be computed exactly. From their expressions it is possible to isolate the Gauss linking number and an invariant of the Milnor type, which describes the topological relations among three or more closed curves.Comment: 16 pages, 1 figure, plain LaTeX + psfig.st

Graded contractions of bilinear invariant forms of Lie algebras

We introduce a new construction of bilinear invariant forms on Lie algebras, based on the method of graded contractions. The general method is described and the $\Bbb Z_2$-, $\Bbb Z_3$-, and $\Bbb Z_2\otimes\Bbb Z_2$-contractions are found. The results can be applied to all Lie algebras and superalgebras (finite or infinite dimensional) which admit the chosen gradings. We consider some examples: contractions of the Killing form, toroidal contractions of $su(3)$, and we briefly discuss the limit to new WZW actions.Comment: 15 page

Exact Black Hole and Cosmological Solutions in a Two-Dimensional Dilaton-Spectator Theory of Gravity

Exact black hole and cosmological solutions are obtained for a special two-dimensional dilaton-spectator ($\phi-\psi$) theory of gravity. We show how in this context any desired spacetime behaviour can be determined by an appropriate choice of a dilaton potential function $V(\phi)$ and a ``coupling function'' $l(\phi)$ in the action. We illustrate several black hole solutions as examples. In particular, asymptotically flat double- and multiple- horizon black hole solutions are obtained. One solution bears an interesting resemblance to the $2D$ string-theoretic black hole and contains the same thermodynamic properties; another resembles the $4D$ Reissner-Nordstrom solution. We find two characteristic features of all the black hole solutions. First the coupling constants in $l(\phi)$ must be set equal to constants of integration (typically the mass). Second, the spectator field $\psi$ and its derivative $\psi^{'}$ both diverge at any event horizon. A test particle with ``spectator charge" ({\it i.e.} one coupled either to $\psi$ or $\psi^{'}$), will therefore encounter an infinite tidal force at the horizon or an ``infinite potential barrier'' located outside the horizon respectively. We also compute the Hawking temperature and entropy for our solutions. In $2D$ $FRW$ cosmology, two non-singular solutions which resemble two exact solutions in $4D$ string-motivated cosmology are obtained. In addition, we construct a singular model which describes the $4D$ standard non-inflationary big bang cosmology ($big-bang\rightarrow radiation\rightarrow dust$). Motivated by the similaritiesbetween $2D$ and $4D$ gravitational field equations in $FRW$ cosmology, we briefly discuss a special $4D$ dilaton-spectator action constructed from the bosonic part of the low energy heterotic string action andComment: 34 pgs. Plain Tex, revised version contains some clarifying comments concerning the relationship between the constants of integration and the coupling constants

Entropy and Action of Dilaton Black Holes

We present a detailed calculation of the entropy and action of $U(1)~2$ dilaton black holes, and show that both quantities coincide with one quarter of the area of the event horizon. Our methods of calculation make it possible to find an explanation of the rule $S = A/4$ for all static, spherically symmetric black holes studied so far. We show that the only contribution to the entropy comes from the extrinsic curvature term at the horizon, which gives $S = A/4$ independently of the charge(s) of the black hole, presence of scalar fields, etc. Previously, this result did not have a general explanation, but was established on a case-by-case basis. The on-shell Lagrangian for maximally supersymmetric extreme dilaton black holes is also calculated and shown to vanish, in agreement with the result obtained by taking the limit of the expression obtained for black holes with regular horizon.The physical meaning of the entropy is discussed in relation to the issue of splitting of extreme black holes.Comment: 15 p., SU-ITP-92-2

Markbooks

A collection of carefully left traces — and their occasionally accompanying thoughts — Markbooks is the result of “an ongoing conversation about attention, its ecologies, its forms, and the markings of its passage.” “For many of the authors included here, the practice of making — and then reading — their little book located them in time… [T]here is paper, and there are pencils, and there are bodies to mark their own motion.

A solution to the mu problem in the presence of a heavy gluino LSP

In this paper we present a solution to the $\mu$ problem in an SO(10) supersymmetric grand unified model with gauge mediated and D-term supersymmetry breaking. A Peccei-Quinn symmetry is broken at the messenger scale $M\sim 10^{12}$ GeV and enables the generation of the $\mu$ term. The boundary conditions defined at $M$ lead to a phenomenologically acceptable version of the minimal supersymmetric standard model with novel particle phenomenology. Either the gluino or the gravitino is the lightest supersymmetric particle (LSP). If the gravitino is the LSP, then the gluino is the next-to-LSP (NLSP) with a lifetime on the order of one month or longer. In either case this heavy gluino, with mass in the range 25 - 35 GeV, can be treated as a stable particle with respect to experiments at high energy accelerators. Given the extensive phenomenological constraints we show that the model can only survive in a narrow region of parameter space resulting in a light neutral Higgs with mass $\sim 86 - 91$ GeV and $\tan\beta \sim 9 - 14$. In addition the lightest stop and neutralino have mass $\sim 100 - 122$ GeV and $\sim 50 - 72$ GeV, respectively. Thus the model will soon be tested. Finally, the invisible axion resulting from PQ symmetry breaking is a cold dark matter candidate.Comment: 30 pages, 9 figure

Hidden Simplicity of Gauge Theory Amplitudes

These notes were given as lectures at the CERN Winter School on Supergravity, Strings and Gauge Theory 2010. We describe the structure of scattering amplitudes in gauge theories, focussing on the maximally supersymmetric theory to highlight the hidden symmetries which appear. Using the BCFW recursion relations we solve for the tree-level S-matrix in N=4 super Yang-Mills theory, and describe how it produces a sum of invariants of a large symmetry algebra. We review amplitudes in the planar theory beyond tree-level, describing the connection between amplitudes and Wilson loops, and discuss the implications of the hidden symmetries.Comment: 46 pages, 15 figures. v2 ref added, typos fixe

Algebra of Lax Connection for T-Dual Models

We study relation between T-duality and integrability. We develop the Hamiltonian formalism for principal chiral model on general group manifold and on its T-dual image. We calculate the Poisson bracket of Lax connections in T-dual model and we show that they are non-local as opposite to the Poisson brackets of Lax connection in original model. We demonstrate these calculations on two specific examples: Sigma model on S(2) and sigma model on AdS(2).Comment: 24 pages, references adde

Anatomy of a mixed bioclastic–siliciclastic regressive tidal sand ridge: Facies-based case study from the lower Pleistocene Siderno Strait, southern Italy

Sand ridges, a common feature of modern open shelves, reflect persistent currents and sediment availability under recent transgressive conditions. They represent the largest bedforms in the oceans and, as such, can yield information on long-term oceanographic processes. However, there is a limited number of tidal sand ridges documented from the rock record, examples of regressive tidal sand ridges are scarce and studies describing ridges in straits are even more rare. This study analyses a Gelasian succession within a structurally controlled, tide-dominated strait in the Siderno Basin, southern Italy. The strait connected two wider basins, and accumulated sediments reworked by amplified tidal (bi-directional) currents. A series of tidal sand ridges with superimposed dunes developed close to the south-eastern end of the strait, where bathymetry was deeper and flow expansion occurred. One of the best-exposed tidal sand ridges, 65 m thick, crops out along a ca 2 km long cliff. Large-scale, ESE-prograding, seaward-offlapping shingles contain sets of bioclastic–siliciclastic, coarse-grained, cross-stratified sandstones, erosionally overlying upper Pliocene shelf marls and fine-grained sandstones. Cross-strata show angular, tangential and sigmoidal foresets with compound architectures and a SSE migration, i.e. oblique to the main growth direction. Fossil content indicates open-marine conditions. The succession changes abruptly across an erosion surface to non-tidal, highly burrowed mixed siliciclastic–bioclastic fine-grained sandstones, less than 15 m thick. Documented features reflect stages of nucleation, active accretion and abandonment of an individual sand ridge, during a complete cycle of relative sea-level change. The ridge formed during a phase of normal regression, with accretion occurring during an initial highstand and the ensuing falling stage. During the lowstand the ridge was split into several minor bodies by enhanced tidal currents. The ensuing transgression draped the moribund ridge with tabular strata, whereas final highstand shelf sedimentation reworked the top of the underlying sand body with weak currents

On the Rotating Charged Black String Solution

A rotating charged black string solution in the low energy effective field theory describing five dimensional heterotic string theory is constructed. The solution is labelled by mass, electric charge, axion charge and angular momentum per unit length. The extremal limit of this solution is also studied.Comment: 12 pages, IMSC-93/6,(Phyzzx macro), January 199