3,595 research outputs found
Increasing the Reliability of Adaptive Quadrature Using Explicit Interpolants
We present two new adaptive quadrature routines. Both routines differ from
previously published algorithms in many aspects, most significantly in how they
represent the integrand, how they treat non-numerical values of the integrand,
how they deal with improper divergent integrals and how they estimate the
integration error. The main focus of these improvements is to increase the
reliability of the algorithms without significantly impacting their efficiency.
Both algorithms are implemented in Matlab and tested using both the "families"
suggested by Lyness and Kaganove and the battery test used by Gander and
Gautschi and Kahaner. They are shown to be more reliable, albeit in some cases
less efficient, than other commonly-used adaptive integrators.Comment: 32 pages, submitted to ACM Transactions on Mathematical Softwar
Inhomogeneous Condensates in Planar QED
We study the formation of vacuum condensates in dimensional QED in the
presence of inhomogeneous background magnetic fields. For a large class of
magnetic fields, the condensate is shown to be proportional to the
inhomogeneous magnetic field, in the large flux limit. This may be viewed as a
{\it local} form of the {\it integrated} degeneracy-flux relation of Aharonov
and Casher.Comment: 13 pp, LaTeX, no figures; to appear in Phys. Rev.
A Note on Asymptotic Freedom at High Temperatures
This short note considers, within the external field approach outlined in
hep-ph/0202026, the role of the lowest lying gluon Landau mode in QCD in the
high temperature limit. Its influence on a temperature- and field-dependent
running coupling constant is examined. The thermal imaginary part of the mode
is temperature-independent in our approach and exactly cancels the well-known
zero temperature imaginary part, thus rendering the Savvidy vacuum stable.
Combining the real part of the mode with the contributions from the higher
lying Landau modes and the vacuum contribution, a field-independent coupling
alpha_s(T) is obtained. It can be interpreted as the ordinary zero temperature
running coupling constant with average thermal momenta \approx 2pi T for
gluons and \approx pi T for quarks.Comment: 4 pages; minor changes, version to appear in Phys. Rev.
"Cold Melting" of Invar Alloys
An anomalously strong volume magnetostriction in Invars may lead to a
situation when at low temperatures the dislocation free energy becomes negative
and a multiple generation of dislocations becomes possible. This generation
induces a first order phase transition from the FCC crystalline to an amorphous
state, and may be called "cold melting". The possibility of the cold melting in
Invars is connected with the fact that the exchange energy contribution into
the dislocation self energy in Invars is strongly enhanced, as compared to
conventional ferromagnetics, due to anomalously strong volume magnetostriction.
The possible candidate, where this effect can be observed, is a FePt disordered
Invar alloy in which the volume magnetostriction is especially large
The impulsive horse:Comparing genetic, physiological and behavioral indicators to those of human addiction.
"An effective two dimensionality" cases bring a new hope to the Kaluza-Klein[like] theories
One step towards realistic Kaluza-Klein[like] theories and a loop hole
through the Witten's "no-go theorem" is presented for cases which we call an
effective two dimensionality cases: In the equations of motion following
from the action with the linear curvature leave spin connections and zweibeins
undetermined. We present the case of a spinor in compactified on a
formally infinite disc with the zweibein which makes a disc curved on an almost
and with the spin connection field which allows on such a sphere only one
massless normalizable spinor state of a particular charge, which couples the
spinor chirally to the corresponding Kaluza-Klein gauge field. We assume no
external gauge fields. The masslessness of a spinor is achieved by the choice
of a spin connection field (which breaks parity), the zweibein and the
normalizability condition for spinor states, which guarantee a discrete
spectrum forming the complete basis. We discuss the meaning of the hole, which
manifests the noncompactness of the space.Comment: 26 pages, 1 figure, an addition which helps to clarify the
assumptions and their consequences (the discreteness of spectrum, the
massless solution of one handedness,..
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