arXiv subjects

J. C. Breckenridge

Publications and source records attributed to J. C. Breckenridge.

8 recordsLinked to original sources

arXiv1997

Black Holes in String Theory

The black hole solutions to Einstein's vacuum field equations are also solutions to the equations of motion of the low energy limit of superstring theory. At the same time, string theory boasts a much broader and richer collection of black hole solutions. Fortunately, string theories also possess a remarkable set of duality symmetries relating states within and between different string theories. These duality symmetries can be exploited to construct new black hole solutions from known solutions, giving us powerful tools with which to explore the black hole solutions of string theory. Here we introduce and demonstrate these techniques of solution generating.

hep-th↗

arXiv1997

QCD Sum Rules and the Pi(1300) Resonance

Global fits to the shape of the first QCD Laplace sum rule exhibiting sensitivity to pion-resonance [$Π(1300)$] parameters are performed, leading to predictions for the pion-resonance mass and decay constant. Two scenarios are considered which differ only in their treatment of the dimension-six quark condensate $< O_6>$. The first scenario assumes an effective scale for $< O_6>$ from other sum-rule applications which is assumed to be independent of the physical value of the quark mass, while the second scenario requires self-consistency between the value of $< O_6>$ and the current algebra constraint $2m< \bar q q>=-f_π^2m_π^2$. Predictions of the pion-resonance mass $M_π$ and decay constant $F_π$ are obtained in these two scenarios. A byproduct of this analysis is a prediction of the renormalization-group invariant quark mass $(\hat m_u+\hat m_d)/2$.

hep-ph↗

arXiv1997

QCD Laplace Sum Rules and the $Π(1300)$ Resonance

A global fit to the shape of the first QCD Laplace sum rule exhibiting sensitivity to pion-resonance [$Π(1300)$] parameters is performed, leading to predictions for the pion-resonance mass and decay constant. This fit leads to predictions of $M_π = 1.15 \pm 0.15 GeV$ for the pion-resonance mass, and $F_π^2=(4.5\pm 2.1).(f_π^2m_π^4/M_π^4)$ for the pion-resonance decay constant.

hep-ph↗

arXiv1997

New angles on D-branes

A low-energy background field solution is presented which describes several D-membranes oriented at angles with respect to one another. The mass and charge densities for this configuration are computed and found to saturate the BPS bound, implying the preservation of one-quarter of the supersymmetries. T-duality is exploited to construct new solutions with nontrivial angles from the basic one.

hep-th↗

arXiv1996

More D-brane bound states

The low-energy background field solutions corresponding to D-brane bound states which possess a difference in dimension of two are presented. These solutions are constructed using the T-duality map between the type IIA and IIB superstring theories. Since supersymmetry is preserved by T-duality, the bound state solutions retain the supersymmetric properties of the initial (single) D-brane states from which they are produced, i.e., they preserve one half of the supersymmetries.

hep-th↗

arXiv1996

Macroscopic and Microscopic Entropy of Near-Extremal Spinning Black Holes

A seven parameter family of five-dimensional black hole solutions depending on mass, two angular momenta, three charges and the asymptotic value of a scalar field is constructed. The entropy is computed as a function of these parameters both from the Bekenstein-Hawking formula and from the degeneracies of the corresponding D-brane states in string theory. The expressions agree at and to leading order away from extremality.

hep-th↗

arXiv1996

D--branes and Spinning Black Holes

We obtain a new class of spinning charged extremal black holes in five dimensions, considered both as classical configurations and in the Dirichlet(D)--brane representation. The degeneracy of states is computed from the D--brane side and the entropy agrees perfectly with that obtained from the black hole side.

hep-th↗

arXiv1994

The Nielsen Identities for the Two-Point Functions of QED and QCD

We consider the Nielsen identities for the two-point functions of full QCD and QED in the class of Lorentz gauges. For pedagogical reasons the identities are first derived in QED to demonstrate the gauge independence of the photon self-energy, and of the electron mass shell. In QCD we derive the general identity and hence the identities for the quark, gluon and ghost propagators. The explicit contributions to the gluon and ghost identities are calculated to one-loop order, and then we show that the quark identity requires that in on-shell schemes the quark mass renormalisation must be gauge independent. Furthermore, we obtain formal solutions for the gluon self-energy and ghost propagator in terms of the gauge dependence of other, independent Green functions.

hep-th↗