3,263 research outputs found
Fermion Determinants
The current status of bounds on and limits of fermion determinants in two,
three and four dimensions in QED and QCD is reviewed. A new lower bound on the
two-dimensional QED determinant is derived. An outline of the demonstration of
the continuity of this determinant at zero mass when the background magnetic
field flux is zero is also given.Comment: 10 page
Finite element analysis of wrinkling membranes
The development of a nonlinear numerical algorithm for the analysis of stresses and displacements in partly wrinkled flat membranes, and its implementation on the SAP VII finite-element code are described. A comparison of numerical results with exact solutions of two benchmark problems reveals excellent agreement, with good convergence of the required iterative procedure. An exact solution of a problem involving axisymmetric deformations of a partly wrinkled shallow curved membrane is also reported
Finite element analysis of wrinkling membranes
The finite element analysis of wrinkling membranes was investigated. The determination of stresses and deformations within large partly wrinkled membrane surfaces is a problem of significant technical interest in such areas as conceptual design and analysis of ultra lightweight spacecraft structures. A closed-form solution to an axisymmetric problem involving partial wrinkling of an inflated shallow membrane was obtained. In particular, a membrane in the shape of a sperical annulus was considered. The outer edge of the annulus was assumed to be fixed so that no displacements occur along the outer perimeter. The inner edge is assumed to be clamped to a rigid movable plug. Solutions for the complete stress, strain, and displacement fields under the assumption of inextensional material behavior are presented for the case of pure torsional loads applied to the plug, and for the case of pure axial loads applied to the plug
Classical capacity of bosonic broadcast communication and a new minimum output entropy conjecture
Previous work on the classical information capacities of bosonic channels has
established the capacity of the single-user pure-loss channel, bounded the
capacity of the single-user thermal-noise channel, and bounded the capacity
region of the multiple-access channel. The latter is a multi-user scenario in
which several transmitters seek to simultaneously and independently communicate
to a single receiver. We study the capacity region of the bosonic broadcast
channel, in which a single transmitter seeks to simultaneously and
independently communicate to two different receivers. It is known that the
tightest available lower bound on the capacity of the single-user thermal-noise
channel is that channel's capacity if, as conjectured, the minimum von Neumann
entropy at the output of a bosonic channel with additive thermal noise occurs
for coherent-state inputs. Evidence in support of this minimum output entropy
conjecture has been accumulated, but a rigorous proof has not been obtained. In
this paper, we propose a new minimum output entropy conjecture that, if proved
to be correct, will establish that the capacity region of the bosonic broadcast
channel equals the inner bound achieved using a coherent-state encoding and
optimum detection. We provide some evidence that supports this new conjecture,
but again a full proof is not available.Comment: 13 pages, 7 figure
Some New/Old Approaches to QCD
This is a talk delivered at the Meeting on Integrable Quantum Field Theories,
Villa Olmo and at STRINGS 1992, Rome, September 1992. I discuss some recent
attempts to revive two old ideas regarding an analytic approach to QCD-the
development of a string representation of the theory and the large N limit of
QCD.Comment: 20 page
Duality in a fermion-like formulation for the electromagnetic field
We employ the Dirac-like equation for the gauge field proposed by Majorana to
obtain an action that is symmetric under duality transformation. We also use
the equivalence between duality and chiral symmetry in this fermion-like
formulation to show how the Maxwell action can be seen as a mass term.Comment: 4 pages. Revtex. Final version to be published in Phys. Rev.
Parity Conservation in Supersymmetric Vector-Like Theories
We show that parity is conserved in vector-like supersymmetric theories, such
as supersymmetric QCD with massive quarks with no cubic couplings among chiral
multiplets, based on fermionic path-integrals, originally developed by Vafa and
Witten. We also look into the effect of supersymmetric breaking through gluino
masses, and see that the parity-conservation is intact also in this case. Our
conclusion is valid, when only bosonic parity-breaking observable terms are
considered in path-integrals like the original Vafa-Witten formulation.Comment: 14 pages, latex, no figures; replaced with corrections of exponent in
old eq.(2.8), misleading expressions in (3.19), comments on fermionic
parity-breaking terms, and some references adde
Baryon Structure and the Chiral Symmetry of QCD
Beyond the spontaneous chiral symmetry breaking scale light and strange
baryons should be considered as systems of three constituent quarks with an
effective confining interaction and a chiral interaction that is mediated by
the octet of Goldstone bosons (pseudoscalar mesons) between the constituent
quarks.Comment: Lecture given at the 35. Universit\"atswochen f\"ur Kern- und
Teilchenphysik, Schladming, Austria, March 1996 (Perturbative and
Nonperturbative Aspects of Quantum Field Theory, ed. by H. Latal and W.
Schweiger, Springer 1996). Paper (23 pages) with 2 figures and the required
macro lamuphy
Positive Parity Scalar Mesons in the 1-2 GeV Mass Range
Based on the observation that K_0(1430) is lighter than its SU_3 counterpart,
a_0(1450), we examine the possibility that these particles, together with
f_0(1370), f_0(1500) and f_0(1710), fill a tetraquark recurrence of the sub-GeV
0^{++} nonet mixed with a glueball state. We find the picture to be consistent
with the known data about the three f_0 resonances, more than the q-qbar
hypothesis. Conventional spin-orbit coupling suggests the q-qbar, P-wave, nonet
to lie around 1200 MeV. We review possible experimental indications of a scalar
isovector resonance at 1.29 GeV, first observed by OBELIX in p-pbar
annihilation.Comment: 12 pages, 9 figures. Extended version. References added. Results and
conclusions unchange
A partial wave analysis of the centrally produced K+K- and K0K0 systems in pp interactions at 450 GeV/c and new information on the spin of the fJ(1710)
A partial wave analysis of the centrally produced K+K- and K0K0 channels has
been performed in pp collisions using an incident beam momentum of 450 GeV/c.
An unambiguous physical solution has been found in each channel. The striking
feature is the observation of peaks in the S-wave corresponding to the f0(1500)
and fJ(1710) with J = 0. The D-wave shows evidence for the f2(1270)/a2(1320),
the f2(1525) and the f2(2150) but there is no evidence for a statistically
significant contribution in the D-wave in the 1.7 GeV mass region.Comment: 15 pages, Latex, 5 Figure
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