7,550 research outputs found
REIT Stock Repurchases: Completion Rates, Long - Run Returns, and the Straddle Hypothesis
This study of real estate investment trusts (REITs) analyzes three possible explanations for the stock price reaction to a repurchase announcement and the subsequent repurchase behavior of managers under each hypothesis. Two of the hypotheses, the signaling hypothesis and the exchange option hypothesis, are established in the existing literature; the third hypothesis is a modification of the exchange option hypothesis. The exchange option hypothesis is extended to allow for additional flexibility in management decisions. This extended exchange option hypothesis is termed the ââstraddleââ hypothesis because it provides management with both a call and put option. The empirical analyses show the straddle hypothesis is a more robust explanation of changes in shares outstanding in the postannouncement period than the alternative explanations.
Auxiliary field method and analytical solutions of the Schr\"{o}dinger equation with exponential potentials
The auxiliary field method is a new and efficient way to compute approximate
analytical eigenenergies and eigenvectors of the Schr\"{o}dinger equation. This
method has already been successfully applied to the case of central potentials
of power-law and logarithmic forms. In the present work, we show that the
Schr\"{o}dinger equation with exponential potentials of the form can also be analytically solved by using the
auxiliary field method. Formulae giving the critical heights and the energy
levels of these potentials are presented. Special attention is drawn on the
Yukawa potential and the pure exponential one
Radiative diagnostics for sub-Larmor scale magnetic turbulence
Radiative diagnostics of high-energy density plasmas is addressed in this
paper. We propose that the radiation produced by energetic particles in
small-scale magnetic field turbulence, which can occur in laser-plasma
experiments, collisionless shocks, and during magnetic reconnection, can be
used to deduce some properties of the turbulent magnetic field. Particles
propagating through such turbulence encounter locally strong magnetic fields,
but over lengths much shorter than a particle gyroradius. Consequently, the
particle is accelerated but not deviated substantially from a straight line
path. We develop the general jitter radiation solutions for this case and show
that the resulting radiation is directly dependent upon the spectral
distribution of the magnetic field through which the particle propagates. We
demonstrate the power of this approach in considering the radiation produced by
particles moving through a region in which a (Weibel-like) filamentation
instability grows magnetic fields randomly oriented in a plane transverse to
counterstreaming particle populations. We calculate the spectrum as would be
seen from the original particle population and as could be seen by using a
quasi-monoenergetic electron beam to probe the turbulent region at various
angles to the filamentation axis.Comment: 17 pages, 4 figures, submitted to Phys. Plasma
Integral equation formulation of the spinless Salpeter equation
The spinless Salpeter equation presents a rather particular differential
operator. In this paper we rewrite this equation into integral and
integro-differential equations. This kind of equations are well known and can
be more easily handled. We also present some analytical results concerning the
spinless Salpeter equation and the action of the square-root operator.Comment: 13 pages, no figure. ReVTeX file. To appear in J. MATH. PHY
Moving boundary approximation for curved streamer ionization fronts: Solvability analysis
The minimal density model for negative streamer ionization fronts is
investigated. An earlier moving boundary approximation for this model consisted
of a "kinetic undercooling" type boundary condition in a Laplacian growth
problem of Hele-Shaw type. Here we derive a curvature correction to the moving
boundary approximation that resembles surface tension. The calculation is based
on solvability analysis with unconventional features, namely, there are three
relevant zero modes of the adjoint operator, one of them diverging;
furthermore, the inner/outer matching ahead of the front has to be performed on
a line rather than on an extended region; and the whole calculation can be
performed analytically. The analysis reveals a relation between the fields
ahead and behind a slowly evolving curved front, the curvature and the
generated conductivity. This relation forces us to give up the ideal
conductivity approximation, and we suggest to replace it by a constant
conductivity approximation. This implies that the electric potential in the
streamer interior is no longer constant but solves a Laplace equation; this
leads to a Muskat-type problem.Comment: 22 pages, 6 figure
Necessary and sufficient conditions for existence of bound states in a central potential
We obtain, using the Birman-Schwinger method, a series of necessary
conditions for the existence of at least one bound state applicable to
arbitrary central potentials in the context of nonrelativistic quantum
mechanics. These conditions yield a monotonic series of lower limits on the
"critical" value of the strength of the potential (for which a first bound
state appears) which converges to the exact critical strength. We also obtain a
sufficient condition for the existence of bound states in a central monotonic
potential which yield an upper limit on the critical strength of the potential.Comment: 7 page
Analytical Solution of the Relativistic Coulomb Problem with a Hard-Core Interaction for a One-Dimensional Spinless Salpeter Equation
In this paper, we construct an analytical solution of the one-dimensional spinless Salpeter equation with a Coulomb potential supplemented by a hard core interaction, which keeps the particle in the x positive region
Hydrogen atom as an eigenvalue problem in 3D spaces of constant curvature and minimal length
An old result of A.F. Stevenson [Phys. Rev.} 59, 842 (1941)] concerning the
Kepler-Coulomb quantum problem on the three-dimensional (3D) hypersphere is
considered from the perspective of the radial Schr\"odinger equations on 3D
spaces of any (either positive, zero or negative) constant curvature. Further
to Stevenson, we show in detail how to get the hypergeometric wavefunction for
the hydrogen atom case. Finally, we make a comparison between the ``space
curvature" effects and minimal length effects for the hydrogen spectrumComment: 6 pages, v
- âŠ