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C. P. Burgess

Publications and source records attributed to C. P. Burgess.

At least 199 records · Page 11Linked to original sources
arXiv1999

Derivation of the Semi-circle Law from the Law of Corresponding States

We show that, for the transition between any two quantum Hall states, the semi-circle law and the existence of a duality symmetry follow solely from the consistency of the law of corresponding states with the two-dimensional scaling flow. This puts these two effects on a sound theoretical footing, implying that both should hold exactly at zero temperature, independently of the details of the microscopic electron dynamics. This derivation also shows how the experimental evidence favours taking the two-dimensional flow seriously for the whole transition, and not just near the critical points.

cond-mat.mes-hall↗
arXiv1999

Solar Neutrinos and the Eclipse Effect

The solar neutrino counting rate in a real time detector like Super--Kamiokanda, SNO, or Borexino is enhanced due to neutrino oscillations in the Moon during a partial or total solar eclipse. The enhancement is calculated as a function of the neutrino parameters in the case of three flavor mixing. This enhancement, if seen, can further help to determine the neutrino parameters.

hep-ph↗
arXiv1999

The Free Energy of N=4 Super-Yang-Mills and the AdS/CFT Correspondence

We compute the high-temperature limit of the free energy for four-dimensional N=4 supersymmetric SU(N_c) Yang-Mills theory. At weak coupling we do so for a general ultrastatic background spacetime, and in the presence of slowly-varying background gauge fields. Using Maldacena's conjectured duality, we calculate the strong-coupling large-N_c expression for the special case that the three-space has constant curvature. We compare the two results paying particular attention to curvature corrections to the leading order expressions.

hep-th↗
arXiv1999

Neutrino Propagation Through Fluctuating Media

The description of neutrino propagation through a fluctuating medium is summarized. Fluctuation-Dissipation-Theorem arguments relate microscopic fluctuations to thermodynamic quantities, allowing these to be very generally studied in astrophysical environments. Fluctuation-induced modifications to neutrino oscillations have been studied in detail within the Sun and within the envelope of supernovae, and although surprisingly large effects have been found none appear to be observable in the near future.

hep-ph↗
arXiv1999

A Goldstone Boson Primer

These lectures are an extremely condensed version of the theory of Goldstone bosons, with general features illustrated using a simple model. A more comprehensive version of these lectures, which includes a general discussion of effective theories of Goldstone bosons, including applications to the low-energy behaviour of pions, spin waves (in antiferromagnets and ferromagnets), and to the SO(5) proposal for high-T_c superconductors may be found in hep-th/9808176.

hep-ph↗
arXiv1998

On the Implications of Discrete Symmetries for the Beta Function of Quantum Hall Systems

We argue that the large discrete symmetry group of quantum Hall systems is insufficient in itself to determine the complete beta function for the scaling of the conductivities, $σ_{xx}$ and $σ_{xy}$. We illustrate this point by showing that a recent ansatz for this function is one of a many-parameter family. A clean prediction for the delocalization exponents for these systems therefore requires the specification of more information, such as past proposals that the beta function is either holomorphic or quasi-holomorphic in the variable $z = (\hbar/e^2)(σ_{xy} + iσ_{xx})$.

cond-mat.mes-hall↗
arXiv1998

An Ode to Effective Lagrangians

A brief introduction is given to the methods and spirit of effective lagrangians. The emphasis is on a summary of the overall picture, using a simple model as the vehicle to motivate and illustrate the main points. Powercounting is illustrated by estimating the size of the quantum corrections to the predictions of classical gravity.

hep-ph↗
arXiv1998

Spacetime Duality and Superduality

We introduce a new class of duality symmetries amongst quantum field theories. The new class is based upon global spacetime symmetries, such as Poincare invariance and supersymmetry, in the same way as the existing duality transformations are based on global internal symmetries. We illustrate these new duality transformations by dualizing several scalar and spin-half theories in 1+1 spacetime dimensions, involving nonsupersymmetric as well as (1,1) and (2,2) supersymmetric models. For (2,2) models the new duality transformations can interchange chiral and twisted-chiral multiplets.

hep-th↗
arXiv1998

Strings at the Intermediate Scale, or is the Fermi Scale Dual to the Planck Scale?

We show that if the string scale is identifed with the intermediate scale, $M_s=\sqrt{M_W M_{Planck}} \sim 10^{11}$ GeV, then the notorious hierarchy, $M_W/M_{Planck} \sim 10^{-16}$, can be explained using only $M_c/M_s \sim 0.01 \sim α_{GUT} $ as small input parameters, where $M_c$ is the compactification scale. This is possible for weakly-coupled Type-I open-string vacua if the observed world is assumed to live in an N=1 supersymmetric 3-brane sector coupled to a separate, hidden, 3-brane world which breaks supersymmetry, because for such a model $M_W/M_{Planck} = 1/2 α_{GUT}^2 (M_c/M_s)^6$. We discuss some of the phenomenological issues presented by such an intermediate-scale string, showing that its benefits include: (i) the possibility of logarithmic gauge-coupling unification of the SM couplings at $M_s$; (ii) a natural axionic solution to the strong-CP problem with a phenomenologically-acceptable Peccei-Quinn scale; (iii) experimentally-interesting neutrino masses, and more.

hep-ph↗
arXiv1998

Supersymmetric Models with Product Groups and Field Dependent Gauge Couplings

We study the dilaton-dependence of the effective action for N=1, SU(N1) x SU(N2) models with one generation of vectorlike matter transforming in the fundamental of both groups. We treat in detail the confining and Coulomb phases of these models writing explicit expressions in many cases for the effective superpotential. We can do so for the Wilson superpotentials of the Coulomb phase when N2=2, N1=2,4. In these cases the Coulomb phase involves a single U(1) gauge multiplet, for which we exhibit the gauge coupling in terms of the modulus of an elliptic curve. The SU(4) x SU(2) model reproduces the weak-coupling limits in a nontrivial way. In the confining phase of all of these models, the dilaton superpotential has a runaway form, but in the Coulomb phase the dilaton enjoys flat directions. Had we used the standard moduli-space variables: Tr M^k, k=1,..., N2, with M the quark condensate matrix, to parameterize the flat directions instead of the eigenvalues of M, we would find physically unacceptable behaviour, illustrating the importance to correctly identify the moduli.

hep-th↗
arXiv1998

Massive-Scalar Effective Actions on Anti-de Sitter Spacetime

Closed forms are derived for the effective actions for free, massive spinless fields in anti-de Sitter spacetimes in arbitrary dimensions. The results have simple expressions in terms of elementary functions (for odd dimensions) or multiple Gamma functions (for even dimensions). We use these to argue against the quantum validity of a recently-proposed duality relating such theories with differing masses and cosmological constants.

hep-th↗
arXiv1998

Constant versus Field Dependent Gauge Couplings in Supersymmetric Theories

We briefly discuss the differences between considering the gauge coupling as a constant or as a field, the dilaton, in N=1 supersymmetric theories. We emphasize the differences regarding supersymmetry breaking. Recent developments on the nonperturbative dynamics of these theories provide new ideas on the induced dilaton potential and its stabilization.

hep-ph↗
arXiv1997

Solar Fluctuations and the MSW Effect

This talk summarizes the results of recent calculations of how fluctuations within the solar medium can influence resonant neutrino oscillations within the sun. Although initial calculations pointed to helioseismic waves as possibly producing detectable effects, recent more careful calculations show this not to be true. Those features of fluctuations which maximize their influence on neutrino propagation are identified, and are likely to have implications for supernovae and the early universe.

hep-ph↗
arXiv1997

Fixing the Dilaton with Asymptotically Expensive Physics?

We propose a general mechanism for stabilizing the dilaton against runaway to weak coupling. The method is based on features of the effective superpotential which arise for supersymmetric gauge theories which are not asymptotically free. Consideration of the 2PI effective action for bilinear operators of matter and gauge superfields allows one to overcome the obstacles to constructing a nonvanishing superpotential.

hep-th↗
arXiv1997

Neutrino Propagation Through Helioseismic Waves

Motivated by earlier calculations showing large effects when neutrinos propagate through fluctuating media, we perform here a detailed analysis of how density fluctuations in the sun in the form of helioseismic waves can modify the MSW solution to the solar neutrino problem. We find negligible effects for the MSW spectrum, even under extreme circumstances. There are two main reasons why our conclusions differ from earlier analyses. First, most helioseismic waves do not affect neutrino propagation because their amplitude is too small in the MSW resonance region, which is the only region to whose fluctuations neutrinos are sensitive. There is one class of waves which may be subject to an instability, however, and so can have significantly larger amplitudes. But the wavelength for these waves is so long that it invalidates the previous methods of calculation. Our more complete calculation significantly reduces the prediction for their influence on neutrino propagation.

hep-ph↗
arXiv1997

A Microscopic Derivation of the SO(5)-Symmetric Landau-Ginzburg Potential

We construct a microscopic model of electron interactions which gives rise to both superconductivity and antiferromagnetism, and which admits an approximate SO(5) symmetry that relates these two phases. The symmetry can be exact, or it may exist only in the long-wavelength limit, depending on the detailed form of the interactions. We compute the macroscopic Landau-Ginzburg free energy for this model as a function of temperature and doping, by explicitly integrating out the fermions. We find that the resulting phase diagram can resemble that observed for the cuprates, with the antiferromagnetism realized as a spin density wave, whose wavelength might be incommensurate with the lattice spacing away from half filling.

cond-mat.supr-con↗