571,577 research outputs found
Gauge-Invariant and Gauge-Fixed D-Brane Actions
The first part of this paper presents actions for Dirichlet p-branes embedded
in a flat 10-dimensional space-time. The fields of the (p+1)-dimensional
world-volume theories are the 10d space-time coordinates , a pair of
Majorana-Weyl spinors and , and a U(1) gauge field
. The N = 2A or 2B super-Poincare group in ten dimensions is realized
as a global symmetry. In addition, the theories have local symmetries
consisting of general coordinate invariance of the world volume, a local
fermionic symmetry (called ``kappa''), and U(1) gauge invariance. A detailed
proof of the kappa symmetry is given that applies to all cases (p = 0,1, . . .,
9). The second part of the paper presents gauge-fixed versions of these
theories. The fields of the 10d (p = 9) gauge-fixed theory are a single
Majorana-Weyl spinor and the U(1) gauge field . This theory,
whose action turns out to be surprisingly simple, is a supersymmetric extension
of 10d Born-Infeld theory. It has two global supersymmetries: one represents an
unbroken symmetry, and the second corresponds to a broken symmetry for which
is the Goldstone fermion. The gauge-fixed supersymmetric D-brane
theories with can be obtained from the 10d one by dimensional reduction.Comment: 33 pages, latex, no figures; revised as requested by refere
Small Window Overlaps Are Effective Probes of Replica Symmetry Breaking in 3D Spin Glasses
We compute numerically small window overlaps in the three dimensional Edwards
Anderson spin glass. We show that they behave in the way implied by the Replica
Symmetry Breaking Ansatz, that they do not qualitatively differ from the full
volume overlap and do not tend to a trivial function when increasing the
lattice volume. On the contrary we show they are affected by small finite
volume effects, and are interesting tools for the study of the features of the
spin glass phase.Comment: 9 pages plus 5 figure
Volume Dependence of the Pion Mass from Renormalization Group Flows
We investigate finite volume effects on the pion mass and the pion decay
constant with renormalization group (RG) methods in the framework of a
phenomenological model for QCD. An understanding of such effects is important
in order to interpret results from lattice QCD and extrapolate reliably from
finite lattice volumes to infinite volume.
We consider the quark-meson-model in a finite Euclidean 3+1 dimensional
volume. In order to break chiral symmetry in the finite volume, we introduce a
small current quark mass. In the corresponding effective potential for the
meson fields, the chiral O(4)-symmetry is broken explicitly, and the sigma and
pion fields are treated individually. Using the proper-time renormalization
group, we derive renormalization group flow equations in the finite volume and
solve these equations in the approximation of a constant expectation value.
We calculate the volume dependence of pion mass and pion decay constant and
compare our results with recent results from chiral perturbation theory in
finite volume.Comment: 9 pages, 3 figures, talk given at "Hadronic Physics 2004 - Joint
meeting Heidelberg-Liege-Paris-Rostock", to appear in the proceedings, AIP
conference serie
Structural transformations of double-walled carbon nanotube bundle under hydrostatic pressure
Three kinds of the response mechanisms to the external pressure have been
found for double-walled carbon nanotube (DWNT) bundle, depending strongly on
their average radius and symmetry. The small-diameter DWNT bundle undergoes a
small discontinuous volume change, and then deform continuously. The
intermediate-diameter DWNT bundle collapses completely after a structure phase
transition (SPT). Significantly, two SPTs exist for the larger-diameter DWNT
bundle if the outer tube has no or symmetry. It would be
interesting to search for signatures of these different structural
transformations by experimentally investigating mechanical, optical and thermal
response functions of DWNT bundle.Comment: 9 pages, 2 figure
Thermodynamics of rotating self-gravitating systems
We investigate the statistical equilibrium properties of a system of
classical particles interacting via Newtonian gravity, enclosed in a
three-dimensional spherical volume. Within a mean-field approximation, we
derive an equation for the density profiles maximizing the microcanonical
entropy and solve it numerically. At low angular momenta, i.e. for a slowly
rotating system, the well-known gravitational collapse ``transition'' is
recovered. At higher angular momenta, instead, rotational symmetry can
spontaneously break down giving rise to more complex equilibrium
configurations, such as double-clusters (``double stars''). We analyze the
thermodynamics of the system and the stability of the different equilibrium
configurations against rotational symmetry breaking, and provide the global
phase diagram.Comment: 12 pages, 9 figure
Finite size phase transitions in QCD with adjoint fermions
We perform a lattice investigation of QCD with three colors and 2 flavors of
Dirac (staggered) fermions in the adjoint representation, defined on a 4d space
with one spatial dimension compactified, and study the phase structure of the
theory as a function of the size Lc of the compactified dimension. We show that
four different phases take place, corresponding to different realizations of
center symmetry: two center symmetric phases, for large or small values of Lc,
separated by two phases in which center symmetry is broken in two different
ways; the dependence of these results on the quark mass is discussed. We study
also chiral properties and how they are affected by the different realizations
of center symmetry; chiral symmetry, in particular, stays spontaneously broken
at the phase transitions and may be restored at much lower values of the
compactification radius. Our results could be relevant to a recently proposed
conjecture of volume indepedence of QCD with adjoint fermions in the large Nc
limit.Comment: 9 pages, 12 figures; extended discussion about the chiral limit and
the chiral properties; 2 figures and references adde
Gravitational Duality, Branes and Charges
It is argued that D=10 type II strings and M-theory in D=11 have D-5 branes
and 9-branes that are not standard p-branes coupled to anti-symmetric tensors.
The global charges in a D-dimensional theory of gravity consist of a momentum
and a dual D-5 form charge , which is related to the
NUT charge. On dimensional reduction, P gives the electric charge and K the
magnetic charge of the graviphoton. The charge K is constructed and shown to
occur in the superalgebra and BPS bounds in , and leads to a NUT-charge
modification of the BPS bound in D=4. is carried by Kaluza-Klein monopoles,
which can be regarded as D-5 branes. Supersymmetry and U-duality imply that the
type IIB theory has (p,q) 9-branes. Orientifolding with 32 (0,1) 9-branes gives
the type I string, while modding out by a related discrete symmetry with 32
(1,0) 9-branes gives the SO(32) heterotic string. Symmetry enhancement, the
effective world-volume theories and the possibility of a twelve dimensional
origin are discussed.Comment: 54 pages, TeX, Phyzzx Macro. Added referenc
Chiral symmetry breaking in nearly conformal gauge theories
We present new results on chiral symmetry breaking in nearly conformal gauge
theories with fermions in the fundamental representation of the SU(3) color
gauge group. The number of fermion flavors is varied in an extended range below
the conformal window with chiral symmetry breaking () for all
flavors between and . To identify we apply
several methods which include, within the framework of chiral perturbation
theory, the analysis of the Goldstone spectrum in the p-regime and the spectrum
of the fermion Dirac operator with eigenvalue distributions of random matrix
theory in the \eps-regime. Chiral condensate enhancement is observed with
increasing when the electroweak symmetry breaking scale is held fixed
in technicolor language. Important finite-volume consistency checks from the
theoretical understanding of the rotator spectrum of the
-regime are discussed. We also consider these gauge theories at
inside the conformal window. The importance of understanding finite
volume, zero momentum gauge field dynamics inside the conformal window is
pointed out. Staggered lattice fermions with supressed taste breaking are used
throughout the simulations.Comment: 21 pages, 9 figures. Presented at the XXVII International Symposium
on Lattice Field Theory, July 26-31, 2009, Peking University, Beijin
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