34,251 research outputs found
The cadmium electrode: Review of the status of research
Investigations characterizing the negative cadmium electrode used in a nickel cadmium battery cell are summarized with citations to references where more detailed information is available. Emphasis is placed on data pertinent to aerospace applications. An evaluation of some of the published results of cadmium electrode research is included
Folds in 2D String Theories
We study maps from a 2D world-sheet to a 2D target space which include folds.
The geometry of folds is discussed and a metric on the space of folded maps is
written down. We show that the latter is not invariant under area preserving
diffeomorphisms of the target space. The contribution to the partition function
of maps associated with a given fold configuration is computed. We derive a
description of folds in terms of Feynman diagrams. A scheme to sum up the
contributions of folds to the partition function in a special case is suggested
and is shown to be related to the Baxter-Wu lattice model. An interpretation of
folds as trajectories of particles in the adjoint representation of
gauge group in the large limit which interact in an unusual way with the
gauge fields is discussed.Comment: 56 pages, latex, followed by epsf, 13 uuencoded epsf figure
The Conformal Window of deformed CFT's in the planar limit
We discuss in the planar approximation the effect of double-trace
deformations on CFT's. We show that this large class of models posses a
conformal window describing a non-trivial flow between two fixed points of the
renormalization group, and reveal the presence of a resonance which we
associate to the remnant of a dilaton pole. As the conformal window shrinks to
zero measure the theory undergoes a conformal phase transition separating a
symmetric from a nonsymmetric phase. The recently conjectured strongly coupled
branch of non-supersymmetric, non-abelian gauge theories with a large number of
flavors is analyzed in light of these results, and a model for the strong
branch is proposed. Some phenomenological implications in the context of
unparticle physics are also emphasized.Comment: 15 pages PRD class, 2 figures, to be published in PR
Quark-Antiquark Bound States in the Relativistic Spectator Formalism
The quark-antiquark bound states are discussed using the relativistic
spectator (Gross) equations. A relativistic covariant framework for analyzing
confined bound states is developed. The relativistic linear potential developed
in an earlier work is proven to give vanishing meson decay
amplitudes, as required by confinement. The regularization of the singularities
in the linear potential that are associated with nonzero energy transfers (i.e.
) is improved. Quark mass functions that build chiral
symmetry into the theory and explain the connection between the current quark
and constituent quark masses are introduced. The formalism is applied to the
description of pions and kaons with reasonable results.Comment: 31 pages, 16 figure
The stability of the spectator, Dirac, and Salpeter equations for mesons
Mesons are made of quark-antiquark pairs held together by the strong force.
The one channel spectator, Dirac, and Salpeter equations can each be used to
model this pairing. We look at cases where the relativistic kernel of these
equations corresponds to a time-like vector exchange, a scalar exchange, or a
linear combination of the two. Since the model used in this paper describes
mesons which cannot decay physically, the equations must describe stable
states. We find that this requirement is not always satisfied, and give a
complete discussion of the conditions under which the various equations give
unphysical, unstable solutions
Analysis of a unidirectional composite containing broken fibers and matrix damage
An analytical solution is developed for the determination of the stresses and displacements in a unidirectional fiber-reinforced composite containing an arbitrary number of broken fibers as well as longitudinal yielding and splitting of the matrix. The solution is developed using a materials-modeling approach which is based on a shear-lag stress transfer mechanism. The equilibrium equation in the axial direction gives a pair of integral equations which are solved numerically. Excellent agreement is shown to exist between the solution and experimental results for notched unidirectional boron/aluminum laminates without splitting. For brittle matrix composites (i.e. epoxy) equally good results are indicated for both matrix yielding and splitting. For yielding without splitting the fracture strength depends on crack length while for large splitting it is crack length independent
Supersonic quantum communication
When locally exciting a quantum lattice model, the excitation will propagate
through the lattice. The effect is responsible for a wealth of non-equilibrium
phenomena, and has been exploited to transmit quantum information through spin
chains. It is a commonly expressed belief that for local Hamiltonians, any such
propagation happens at a finite "speed of sound". Indeed, the Lieb-Robinson
theorem states that in spin models, all effects caused by a perturbation are
limited to a causal cone defined by a constant speed, up to exponentially small
corrections. In this work we show that for translationally invariant bosonic
models with nearest-neighbor interactions, this belief is incorrect: We prove
that one can encounter excitations which accelerate under the natural dynamics
of the lattice and allow for reliable transmission of information faster than
any finite speed of sound. The effect is only limited by the model's range of
validity (eventually by relativity). It also implies that in non-equilibrium
dynamics of strongly correlated bosonic models far-away regions may become
quickly entangled, suggesting that their simulation may be much harder than
that of spin chains even in the low energy sector.Comment: 4+3 pages, 1 figure, some material added, typographic error fixe
A morphological study of waves in the thermosphere using DE-2 observations
Theoretical model and data analysis of DE-2 observations for determining the correlation between the neutral wave activity and plasma irregularities have been presented. The relationships between the observed structure of the sources, precipitation and joule heating, and the fluctuations in neutral and plasma parameters are obtained by analyzing two measurements of neutral atmospheric wave activity and plasma irregularities by DE-2 during perigee passes at an altitude on the order of 300 to 350 km over the polar cap. A theoretical model based on thermal nonlinearity (joule heating) to give mode-mode coupling is developed to explore the role of neutral disturbance (winds and gravity waves) on the generation of plasma irregularities
The String Theory Approach to Generalized 2D Yang-Mills Theory
We calculate the partition function of the ( and ) generalized
theory defined on an arbitrary Riemann surface. The result which is
expressed as a sum over irreducible representations generalizes the Rusakov
formula for ordinary YM_2 theory. A diagrammatic expansion of the formula
enables us to derive a Gross-Taylor like stringy description of the model. A
sum of 2D string maps is shown to reproduce the gauge theory results. Maps with
branch points of degree higher than one, as well as ``microscopic surfaces''
play an important role in the sum. We discuss the underlying string theory.Comment: TAUP-2182-94, 53 pages of LaTeX and 5 uuencoded eps figure
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