Liquid-gas and other unusual thermal phase transitions in some large-N magnets

Much insight into the low temperature properties of quantum magnets has been gained by generalizing them to symmetry groups of order N, and then studying the large N limit. In this paper we consider an unusual aspect of their finite temperature behavior--their exhibiting a phase transition between a perfectly paramagetic state and a paramagnetic state with a finite correlation length at N = \infty. We analyze this phenomenon in some detail in the large ``spin'' (classical) limit of the SU(N) ferromagnet which is also a lattice discretization of the CP^{N-1} model. We show that at N = \infty the order of the transition is governed by lattice connectivity. At finite values of N, the transition goes away in one or less dimension but survives on many lattices in two dimensions and higher, for sufficiently large N. The latter conclusion contradicts a recent conjecture of Sokal and Starinets, yet is consistent with the known finite temperature behavior of the SU(2) case. We also report closely related first order paramagnet-ferromagnet transitions at large N and shed light on a violation of Elitzur's theorem at infinite N via the large q limit of the q-state Potts model, reformulated as an Ising gauge theory.Comment: 27 pages, 7 figures. Added clarifications requested by a refere

Designing of a Fleet-Leader Program for Carbon Composite Overwrapped Pressure Vessels

Composite Overwrapped Pressure Vessels (COPVs) are often used for storing pressurant gases on board spacecraft when mass saving is a prime requirement. Substantial weight savings can be achieved compared to all metallic pressure vessels. For example, on the space shuttle, replacement of all metallic pressure vessels with Kevlar COPVs resulted in a weight savings of about 30 percent. Mass critical space applications such as the Ares and Orion vehicles are currently being planned to use as many COPVs as possible in place of all-metallic pressure vessels to minimize the overall mass of the vehicle. Due to the fact that overwraps are subjected to sustained loads during long periods of a mission, stress rupture failure is a major concern. It is, therefore, important to ascertain the reliability of these vessels by analysis, since it is practically impossible to show by experimental testing the reliability of flight quality vessels. Also, it is a common practice to set aside flight quality vessels as "fleet leaders" in a test program where these vessels are subjected to slightly accelerated operating conditions so that they lead the actual flight vessels both in time and load. The intention of fleet leaders is to provide advanced warning if there is a serious design flaw in the vessels so that a major disaster in the flight vessels can be averted with advance warning. On the other hand, the accelerating conditions must be not so severe as to be prone to false alarms. The primary focus of the present paper is to provide an analytical basis for designing a viable fleet leader program for carbon COPVs. The analysis is based on a stress rupture behavior model incorporating Weibull statistics and power-law sensitivity of life to fiber stress level

Unparticle Physics in the Moller Scattering

We investigate the virtual effects of vector unparticles in the Moller scattering. We derive the analytic expression for scattering amplitudes with unpolarized beams. We obtain 95% confidence level limits on the unparticle couplings $\lambda_{V}$ and $\lambda_{A}$ with integrated luminosity of $L_{int}=50, 500 fb^{-1}$ and $\sqrt{s}=100, 300$ and 500 GeV energies. We show that limits on $\lambda_{V}$ are more sensitive than $\lambda_{A}$.Comment: 10 pages, 5 figures, 4 table

Tunneling into Extra Dimension and High-Energy Violation of Lorentz Invariance

We consider a class of models with infinite extra dimension, where bulk space does not possess SO(1,3) invariance, but Lorentz invariance emerges as an approximate symmetry of the low-energy effective theory. In these models, the maximum attainable speeds of the graviton, gauge bosons and scalar particles are automatically equal to each other and smaller than the maximum speed in the bulk. Additional fine-tuning is needed in order to assure that the maximum attainable speed of fermions takes the same value. A peculiar feature of our scenario is that there are no truly localized modes. All four-dimensional particles are resonances with finite widths. The latter depends on the energy of the particle and is naturally small at low energies.Comment: 21 pages, references and comments added, final version to appear in JHE

The Effective Action For Brane Localized Gauge Fields

The low energy effective action including gauge field degrees of freedom on a non-BPS p=2 brane embedded in a N=1, D=4 target superspace is obtained through the method of nonlinear realizations of the associated super-Poincare symmetries. The invariant interactions of the gauge fields and the brane excitation modes corresponding to the Nambu-Goldstone degrees of freedom resulting from the broken space translational symmetry and the target space supersymmetries are determined. Brane localized matter field interactions with the gauge fields are obtained through the construction of the combined gauge and super-Poincare covariant derivatives for the matter fields.Comment: 12 pages, no figure

Maximally localized states and causality in non commutative quantum theories

We give simple representations for quantum theories in which the position commutators are non vanishing constants. A particular representation reproduces results found using the Moyal star product. The notion of exact localization being meaningless in these theories, we adapt the notion of ``maximally localized states'' developed in another context . We find that gaussian functions play this role in a 2+1 dimensional model in which the non commutation relations concern positions only. An interpretation of the wave function in this non commutative geometry is suggested. We also analyze higher dimensional cases. A possible incidence on the causality issue for a Q.F.T with a non commuting time is sketched.Comment: 11 pages, Revtex. The presentation has been improved, the subsection on high dimensions has been modified. This version will appear in PR

Quantum Hall Bilayers and the Chiral Sine-Gordon Equation

The edge state theory of a class of symmetric double-layer quantum Hall systems with interlayer electron tunneling reduces to the sum of a free field theory and a field theory of a chiral Bose field with a self-interaction of the sine-Gordon form. We argue that the perturbative renormalization group flow of this chiral sine-Gordon theory is distinct from the standard (non-chiral) sine-Gordon theory, contrary to a previous assertion by Renn, and that the theory is manifestly sensible only at a discrete set of values of the inverse period of the cosine interaction (beta). We obtain exact solutions for the spectra and correlation functions of the chiral sine-Gordon theory at the two values of beta at which the electron tunneling in bilayers is not irrelevant. Of these, the marginal case (beta^2=4) is of greatest interest: the spectrum of the interacting theory is that of two Majorana fermions with different, dynamically generated, velocities. For the experimentally observed bilayer 331 state at filling factor 1/2, this implies the trifurcation of electrons added to the edge. We also present a method for fermionizing the theory at the discrete points (integer beta^2) by the introduction of auxiliary degrees of freedom that could prove useful in other problems involving quantum Hall multilayers.Comment: revtex, epsf; 39 p., 4 figs; corrections to three equations; two-up postscript at http://www.sns.ias.edu/~leonid/csg-2up.p

Spontaneous breaking of Lorentz invariance, black holes and perpetuum mobile of the 2nd kind

We study the effect of spontaneous breaking of Lorentz invariance on black hole thermodynamics. We consider a scenario where Lorentz symmetry breaking manifests itself by the difference of maximal velocities attainable by particles of different species in a preferred reference frame. The Lorentz breaking sector is represented by the ghost condensate. We find that the notions of black hole entropy and temperature loose their universal meaning. In particular, the standard derivation of the Hawking radiation yields that a black hole does emit thermal radiation in any given particle species, but with temperature depending on the maximal attainable velocity of this species. We demonstrate that this property implies violation of the second law of thermodynamics, and hence, allows construction of a perpetuum mobile of the 2nd kind. We discuss possible interpretation of these results.Comment: 13 pages; references adde

Fracture model with variable range of interaction

We introduce a fiber bundle model where the interaction among fibers is modeled by an adjustable stress-transfer function which can interpolate between the two limiting cases of load redistribution, the global and the local load sharing schemes. By varying the range of interaction several features of the model are numerically studied and a crossover from mean field to short range behavior is obtained. The properties of the two regimes and the emergence of the crossover in between are explored by numerically studying the dependence of the ultimate strength of the material on the system size, the distribution of avalanches of breakings, and of the cluster sizes of broken fibers. Finally, we analyze the moments of the cluster size distributions to accurately determine the value at which the crossover is observed.Comment: 8 pages, 8 figures. Two columns revtex format. Final version to be published in Phys. Rev.

No-Hair Theorem for Spontaneously Broken Abelian Models in Static Black Holes

The vanishing of the electromagnetic field, for purely electric configurations of spontaneously broken Abelian models, is established in the domain of outer communications of a static asymptotically flat black hole. The proof is gauge invariant, and is accomplished without any dependence on the model. In the particular case of the Abelian Higgs model, it is shown that the only solutions admitted for the scalar field become the vacuum expectation values of the self-interaction.Comment: 8 pages, 2 figures, RevTeX; some changes to match published versio