1,908 research outputs found
On Lattice QCD with Many Flavors
We discuss the confining and chiral-symmetry breaking properties of QCD with
a large number of flavors . In a Monte Carlo simulation of QCD with staggered fermions, we find clear evidence of a first order bulk phase
transition which separates phases with broken and unbroken chiral symmetry.
This is consistent with extrapolations of earlier studies with smaller ,
and is also as expected from general arguments. Thus, even when the
perturbative renormalization group flow has a new infrared stable fixed point
near the origin, lattice artifacts induce chiral symmetry breaking, and
presumably confinement, at sufficiently strong coupling.Comment: 10 pages, LaTeX, figures part of the LaTeX fil
Black Holes and Five-brane Thermodynamics
The phase diagram for Dp-branes in M-theory compactified on , ,
, and is constructed. As for the lower-dimensional tori considered
in our previous work (hep-th/9810224), the black brane phase at high entropy
connects onto matrix theory at low entropy; we thus recover all known instances
of matrix theory as consequences of the Maldacena conjecture. The difficulties
that arise for are reviewed. We also analyze the D1-D5 system on ;
we exhibit its relation to matrix models of M5-branes, and use spectral flow as
a tool to investigate the dependence of the phase structure on angular
momentum.Comment: 57 pages, 6 eps figures, latex. v2: DLCQ limit of 5-brane corrected;
typos corrected, references added. v3: reference added, typos corrected v4:
comments on DLCQ limit of 5-brane corrected one last time. Final version, to
appear in Phys. Rev.
Almost Ideal Clocks in Quantum Cosmology: A Brief Derivation of Time
A formalism for quantizing time reparametrization invariant dynamics is
considered and applied to systems which contain an `almost ideal clock.'
Previously, this formalism was successfully applied to the Bianchi models and,
while it contains no fundamental notion of `time' or `evolution,' the approach
does contain a notion of correlations. Using correlations with the almost ideal
clock to introduce a notion of time, the work below derives the complete
formalism of external time quantum mechanics. The limit of an ideal clock is
found to be closely associated with the Klein-Gordon inner product and the
Newton-Wigner formalism and, in addition, this limit is shown to fail for a
clock that measures metric-defined proper time near a singularity in Bianchi
models.Comment: 16 pages ReVTeX (35 preprint pages
An E9 multiplet of BPS states
We construct an infinite E9 multiplet of BPS states for 11D supergravity. For
each positive real root of E9 we obtain a BPS solution of 11D supergravity, or
of its exotic counterparts, depending on two non-compact transverse space
variables. All these solutions are related by U-dualities realised via E9 Weyl
transformations in the regular embedding of E9 in E10, E10 in E11. In this way
we recover the basic BPS solutions, namely the KK-wave, the M2 brane, the M5
brane and the KK6-monopole, as well as other solutions admitting eight
longitudinal space dimensions. A novel technique of combining Weyl reflexions
with compensating transformations allows the construction of many new BPS
solutions, each of which can be mapped to a solution of a dual effective action
of gravity coupled to a certain higher rank tensor field. For real roots of E10
which are not roots of E9, we obtain additional BPS solutions transcending 11D
supergravity (as exemplified by the lowest level solution corresponding to the
M9 brane). The relation between the dual formulation and the one in terms of
the original 11D supergravity fields has significance beyond the realm of BPS
solutions. We establish the link with the Geroch group of general relativity,
and explain how the E9 duality transformations generalize the standard Hodge
dualities to an infinite set of `non-closing dualities'.Comment: 76 pages, 6 figure
Shell structure at N=28 near the dripline: spectroscopy of Si, P and S
Measurements of the N=28 isotones 42Si, 43P and 44S using one- and two-proton
knockout reactions from the radioactive beam nuclei 44S and 46Ar are reported.
The knockout reaction cross sections for populating 42Si and 43P and a 184 keV
gamma-ray observed in 43P establish that the d_{3/2} and s_{1/2} proton orbits
are nearly degenerate in these nuclei and that there is a substantial Z=14
subshell closure separating these two orbits from the d_{5/2} orbit. The
increase in the inclusive two-proton knockout cross section from 42Si to 44S
demonstrates the importance of the availability of valence protons for
determining the cross section. New calculations of the two-proton knockout
reactions that include diffractive effects are presented. In addition, it is
proposed that a search for the d_{5/2} proton strength in 43P via a higher
statistics one-proton knockout experiment could help determine the size of the
Z=14 closure.Comment: Phys. Rev. C, in pres
The Asymptotic Dynamics of de Sitter Gravity in three Dimensions
We show that the asymptotic dynamics of three-dimensional gravity with
positive cosmological constant is described by Euclidean Liouville theory. This
provides an explicit example of a correspondence between de Sitter gravity and
conformal field theories. In the case at hand, this correspondence is
established by formulating Einstein gravity with positive cosmological constant
in three dimensions as an SL(2,C) Chern-Simons theory. The de Sitter boundary
conditions on the connection are divided into two parts. The first part reduces
the CS action to a nonchiral SL(2,C) WZNW model, whereas the second provides
the constraints for a further reduction to Liouville theory, which lives on the
past boundary of dS_3.Comment: 12 pages, LaTeX, no figures, v2: Minor changes, references adde
Supersymmetric Homogeneous Quantum Cosmologies Coupled to a Scalar Field
Recent work on supersymmetric Bianchi type IX cosmologies coupled to a
scalar field is extended to a general treatment of homogeneous quantum
cosmologies with explicitely solvable momentum constraints, i.e. Bianchi types
I, II, VII, VIII besides the Bianchi type IX, and special cases, namely the
Friedmann universes, the Kantowski-Sachs space, and Taub-NUT space. Besides the
earlier explicit solution of the Wheeler DeWitt equation for Bianchi type IX,
describing a virtual wormhole fluctuation, an additional explicit solution is
given and identified with the `no-boundary state'.Comment: 23 PAGE
Thermodynamics of entanglement in Schwarzschild spacetime
Extending the analysis in our previous paper, we construct the entanglement
thermodynamics for a massless scalar field on the Schwarzschild spacetime.
Contrary to the flat case, the entanglement energy turns out to be
proportional to area radius of the boundary if it is near the horizon. This
peculiar behavior of can be understood by the red-shift effect caused
by the curved background. Combined with the behavior of the entanglement
entropy, this result yields, quite surprisingly, the entanglement
thermodynamics of the same structure as the black hole thermodynamics. On the
basis of these results, we discuss the relevance of the concept of entanglement
as the microscopic origin of the black hole thermodynamics.Comment: 27 pages, Latex file, 7 figures; revised to clarify our choice of the
state and to add references. Accepted for publication in Physical Review
Chiral symmetry breaking by a non-Abelian external field in (2+1)-dimensions
We investigate the effect of a constant external non-Abelian field on chiral
symmetry breaking in a (2+1)-dimensional Nambu-Jona-Lasinio model and in 3D QCD
by solving the gap equation and the Bethe-Salpeter equation, and also by RG
analysis. In the (2+1)-dimensional NJL model chiral symmetry breaking occurs
for any weak coupling constant but in 3D QCD catalysis of chiral symmetry
breaking does not occur.Comment: 11 pages, RevTe
Effective Action and Conformal Phase Transition in Three-Dimensional QED
The effective action for local composite operators in is considered.
The effective potential is calculated in leading order in ( is the
number of fermion flavors) and used to describe the features of the phase
transition at , . It is shown that this
continuous phase transition satisfies the criteria of the conformal phase
transition, considered recently in the literature. In particular, there is an
abrupt change of the spectrum of light excitations at the critical point,
although the phase transition is continuous, and the structure of the equation
for the divergence of the dilatation current is essentially different in the
symmetric and nonsymmetric phases. The connection of this dynamics with the
dynamics in is briefly discussed.Comment: 17 pages, RevTex file, no figures. The discussion of the effective
action is extende
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