1,649 research outputs found
Tidal Synchronization and Differential Rotation of Kepler Eclipsing Binaries
Few observational constraints exist for the tidal synchronization rate of
late-type stars, despite its fundamental role in binary evolution. We visually
inspected the light curves of 2278 eclipsing binaries (EBs) from the Kepler
Eclipsing Binary Catalog to identify those with starspot modulations, as well
as other types of out-of-eclipse variability. We report rotation periods for
816 EBs with starspot modulations, and find that 79% of EBs with orbital
periods less than ten days are synchronized. However, a population of short
period EBs exists with rotation periods typically 13% slower than synchronous,
which we attribute to the differential rotation of high latitude starspots. At
10 days, there is a transition from predominantly circular, synchronized EBs to
predominantly eccentric, pseudosynchronized EBs. This transition period is in
good agreement with the predicted and observed circularization period for Milky
Way field binaries. At orbital periods greater than about 30 days, the amount
of tidal synchronization decreases. We also report 12 previously unidentified
candidate Scuti and Doradus pulsators, as well as a candidate
RS CVn system with an evolved primary that exhibits starspot occultations. For
short period contact binaries, we observe a period-color relation, and compare
it to previous studies. As a whole, these results represent the largest
homogeneous study of tidal synchronization of late-type stars.Comment: Accepted for publication in the Astronomical Journal. EB rotation
periods and classifications available at
https://github.com/jlurie/decatur/blob/master/decatur/data/final_catalog.cs
Scale effects in tribological properties of solid-lubricating composites made of ultra-high molecular weight polyethylene filled with calcium stearate particles
Friction properties being influenced by scale effects are simulated in the paper by the example of polymer composite material made from Ultra High-Molecular Weight Polyethylenes (UHMWPE) filled by calcium stearate (C[36]H[70]CaO[4]). Of interest are the composites whose mechanical properties and tribotechnical characteristics do not depend monotonically on filler (inclusions) weight fraction. In order to describe the influence of scale effects onto frictional properties the model based on Reiss averaging (model of "weak phase") is employed. It is also suggested that when gradient elasticity theory is applicable the formal analogy between effective friction coefficient for surface heterogeneous structures and effective mechanical properties (compliances) for heterogeneous material can take place. Theoretical dependence to describe nonmonotonic change of effective friction coefficient versus filler concentration was obtained for the polymer composites under study. The suggested expressions might be useful for the sake of properties prognosis of antifriction polymeric materilas
Nucleon-nucleon interaction in the -matrix inverse scattering approach and few-nucleon systems
The nucleon-nucleon interaction is constructed by means of the -matrix
version of inverse scattering theory. Ambiguities of the interaction are
eliminated by postulating tridiagonal and quasi-tridiagonal forms of the
potential matrix in the oscillator basis in uncoupled and coupled waves,
respectively. The obtained interaction is very accurate in reproducing the
scattering data and deuteron properties. The interaction is used in the no-core
shell model calculations of H and He nuclei. The resulting binding
energies of H and He are very close to experimental values.Comment: Text is revised, new figures and references adde
Optimization with partial differential equations in dieudonné-rashevsky form and conjugate problems
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46185/1/205_2004_Article_BF00247693.pd
Inverse scattering J-matrix approach to nucleon-nucleus scattering and the shell model
The -matrix inverse scattering approach can be used as an alternative to a
conventional -matrix in analyzing scattering phase shifts and extracting
resonance energies and widths from experimental data. A great advantage of the
-matrix is that it provides eigenstates directly related to the ones
obtained in the shell model in a given model space and with a given value of
the oscillator spacing . This relationship is of a particular
interest in the cases when a many-body system does not have a resonant state or
the resonance is broad and its energy can differ significantly from the shell
model eigenstate. We discuss the -matrix inverse scattering technique,
extend it for the case of charged colliding particles and apply it to the
analysis of and scattering. The results are compared with
the No-core Shell Model calculations of He and Li.Comment: Some text is added following suggestions of a journal refere
Multi-channel phase-equivalent transformation and supersymmetry
Phase-equivalent transformation of local interaction is generalized to the
multi-channel case. Generally, the transformation does not change the number of
the bound states in the system and their energies. However, with a special
choice of the parameters, the transformation removes one of the bound states
and is equivalent to the multi-channel supersymmetry transformation recently
suggested by Sparenberg and Baye. Using the transformation, it is also possible
to add a bound state to the discrete spectrum of the system at a given energy
if the angular momentum at least in one of the coupled channels .Comment: 9 pages, revtex; to be published in Phys. At. Nucl. (Oct. 2000
Renormalization of the Sigma-Omega model within the framework of U(1) gauge symmetry
It is shown that the Sigma-Omega model which is widely used in the study of
nuclear relativistic many-body problem can exactly be treated as an Abelian
massive gauge field theory. The quantization of this theory can perfectly be
performed by means of the general methods described in the quantum gauge field
theory. Especially, the local U(1) gauge symmetry of the theory leads to a
series of Ward-Takahashi identities satisfied by Green's functions and proper
vertices. These identities form an uniquely correct basis for the
renormalization of the theory. The renormalization is carried out in the
mass-dependent momentum space subtraction scheme and by the renormalization
group approach. With the aid of the renormalization boundary conditions, the
solutions to the renormalization group equations are given in definite
expressions without any ambiguity and renormalized S-matrix elememts are
exactly formulated in forms as given in a series of tree diagrams provided that
the physical parameters are replaced by the running ones. As an illustration of
the renormalization procedure, the one-loop renormalization is concretely
carried out and the results are given in rigorous forms which are suitable in
the whole energy region. The effect of the one-loop renormalization is examined
by the two-nucleon elastic scattering.Comment: 32 pages, 17 figure
Possible retardation effects of quark confinement on the meson spectrum
The reduced Bethe-Salpeter equation with scalar confinement and vector gluon
exchange is applied to quark-antiquark bound states. The so called intrinsic
flaw of Salpeter equation with static scalar confinement is investigated. The
notorious problem of narrow level spacings is found to be remedied by taking
into consideration the retardation effect of scalar confinement. Good fit for
the mass spectrum of both heavy and light quarkomium states is then obtained.Comment: 14 pages in LaTex for
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