1,791 research outputs found
Bounds on Localized Modes in the Crystal Impurity Problem
Using general properties of the crystal site representation normal mode
matrix, we provide some very simple bounds on localized modes in simple,
body-centered and face-centered cubic crystals with substitutional point
defects. We derive a trace condition constraint on the net change in crystal
eigenfrequencies caused by the introduction of a defect, with the condition
being a completely general one which holds for any combination of central and
non-central crystal force-constants and for all-neighbor interactions. Using
this condition we show that the sufficient condition for producing localized
modes in an arbitrary cubic crystal by a mass change at the defect site is that
the defect mass be less than one half of that of the host atom mass which it
replaces, and that the sufficient condition for producing localized modes in an
arbitrary cubic crystal by force-constant changes alone is that the defect site
self force-constant be greater than twice that of the pure crystal self
force-constant of the host atom which it replaces.Comment: 25 pages, 3 figures, revtex4. Updated version contains much more
general bounds than original versio
Bose-Einstein Correlations for Mixed Neutral Mesons
Correlations are shown to arise in nonidentical mixed-particle pairs like
when observed in identical decay modes like in
multiparticle final states containing many partial waves. No enhancement is
found in any single partial wave and all partial wave analyses of the s-wave
threshold resonance and should give the same results for all decay
modes. In CP violation experiments where pairs are inclusively
produced and correlated decays into and leptonic modes are observed,
the CP-violating lepton asymmetry is enhanced by a factor of two in the
kinematic region where Bose enhancement occurs.Comment: 11 page
Framework for Identification of Neutral B Mesons
We introduce a method for the study of CP-violating asymmetries in tagged
states of neutral mesons with arbitrary coherence properties. A set of
time-dependent measurements is identified which completely specifies the
density matrix of the initial state in a two-component space with basis vectors
and , and permits a determination of phases in the
Cabibbo-Kobayashi-Maskawa matrix. For a given tagging configuration, the
measurement of decays both to flavor eigenstates and to CP eigenstates provides
the necessary information.Comment: Submitted to Phys. Rev. Letters. 8 pages, LaTeX, Technion-PH-93-31 /
EFI 93-3
Large N Scaling Behavior of the Lipkin-Meshkov-Glick Model
We introduce a novel semiclassical approach to the Lipkin model. In this way
the well-known phase transition arising at the critical value of the coupling
is intuitively understood. New results -- showing for strong couplings the
existence of a threshold energy which separates deformed from undeformed states
as well as the divergence of the density of states at the threshold energy --
are explained straightforwardly and in quantitative terms by the appearance of
a double well structure in a classical system corresponding to the Lipkin
model. Previously unnoticed features of the eigenstates near the threshold
energy are also predicted and found to hold.Comment: 4 pages, 2 figures, to appear in PR
The Ursinus Weekly, April 27, 1936
Plans completed for open house • Junior week-end is great success • Ball team takes two during week • Glee Club to present annual spring concert • Coaches select cast for Curtain Club play • Installation of WSGA officers held last week • York alumni hold annual banquet and choose officers • E.C. Wagner, Ursinus alumnus, addresses chemical society • Yost\u27s review of Lantern continued from last week • Music clubs to give opera during commencement week • Pageant groups to rehearse according to given schedule • Brotherhood of St. Paul elects new officers for coming year • Herrick B. Young to speak to IRC to-morrow eve • Muhlenberg easily defeats grizzly tennis team, 6-1 • Grizzly J.V.\u27s lose first game of season to Hill School, 7-6 • Track records corrections • Brodbeck tops ball league • TKA names new membershttps://digitalcommons.ursinus.edu/weekly/1959/thumbnail.jp
The Ursinus Weekly, February 22, 1937
Men debaters go on tour of four colleges; women are busy at home throughout week • Student council lays penalties • Sororities pledge flushed freshmen after hectic week • Congressman Ditter to speak at forum • Large crowd hails Curtain Club show • Try-outs for junior play to be held this evening • College receives $18,000 in Sarah Leiphart will • Y panel group discusses negro-versus-white topic • Sociological survey journey is planned for after Easter • Professor Baker speaks at vespers in Bomberger • Yost reviews McClure-Holzknecht Shakespeare set; second vol., just printed, wins graphic arts award • Philadelphia alumni plan banquet; committee meets • Placement bureau reports jobs for seniors, grads • Contest for radio script writing is opened to all major colleges • Hedgerow, praised before, comes to perform again • Lehigh begins new course named general education • Lantern issue will appear in March; copy is solicited • Don Kellett\u27s cubs defeat Penn, 36-30 • Haverford gets close one, Hopkins wins, as injuries still plague bear matmen • Mules hand varsity team its eighth league defeat • Drexel six go down, 34-7, before co-eds\u27 onslaught • Both teams lose battles at Albright on Wednesday • Brotherhood of St. Paul meets; appoints two deputationshttps://digitalcommons.ursinus.edu/weekly/1922/thumbnail.jp
The Gross-Pitaevskii Equation for Bose Particles in a Double Well Potential: Two Mode Models and Beyond
There have been many discussions of two-mode models for Bose condensates in a
double well potential, but few cases in which parameters for these models have
been calculated for realistic situations. Recent experiments lead us to use the
Gross-Pitaevskii equation to obtain optimum two-mode parameters. We find that
by using the lowest symmetric and antisymmetric wavefunctions, it is possible
to derive equations for a more exact two-mode model that provides for a
variable tunneling rate depending on the instantaneous values of the number of
atoms and phase differences. Especially for larger values of the nonlinear
interaction term and larger barrier heights, results from this model produce
better agreement with numerical solutions of the time-dependent
Gross-Pitaevskii equation in 1D and 3D, as compared with previous models with
constant tunneling, and better agreement with experimental results for the
tunneling oscillation frequency [Albiez et al., cond-mat/0411757]. We also show
how this approach can be used to obtain modified equations for a second
quantized version of the Bose double well problem.Comment: RevTeX, 14 pages, 14 figure
Beyond the relativistic mean-field approximation (II): configuration mixing of mean-field wave functions projected on angular momentum and particle number
The framework of relativistic self-consistent mean-field models is extended
to include correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. The generator coordinate method is used
to perform configuration mixing of angular-momentum and particle-number
projected relativistic wave functions. The geometry is restricted to axially
symmetric shapes, and the intrinsic wave functions are generated from the
solutions of the relativistic mean-field + Lipkin-Nogami BCS equations, with a
constraint on the mass quadrupole moment. The model employs a relativistic
point-coupling (contact) nucleon-nucleon effective interaction in the
particle-hole channel, and a density-independent -interaction in the
pairing channel. Illustrative calculations are performed for Mg,
S and Ar, and compared with results obtained employing the model
developed in the first part of this work, i.e. without particle-number
projection, as well as with the corresponding non-relativistic models based on
Skyrme and Gogny effective interactions.Comment: 37 pages, 10 figures, submitted to Physical Review
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