22,717 research outputs found
Partial Dynamical SU(3) Symmetry and the Nature of the Lowest K=0 Collective Excitation in Deformed Nuclei
We discuss the implications of partial dynamical SU(3) symmetry (PDS) for the
structure of the lowest K=0^{+} (K=0_2) collective excitation in deformed
nuclei. We consider an interacting boson model Hamiltonian whose ground and
gamma bands have good SU(3) symmetry while the K=0_2 band is mixed. It is shown
that the double-phonon components in the K=0_2 wave function arise from SU(3)
admixtures which, in turn, can be determined from absolute E2 rates connecting
the K=0_2 and ground bands. An explicit expression is derived for these
admixtures in terms of the ratio of K=0_2 and gamma bandhead energies. The
SU(3) PDS predictions are compared with existing data and with broken-SU(3)
calculations for ^{168}Er.Comment: 12 pages, 2 figure
Precedence-type Test based on Progressively Censored Samples
In this paper, we introduce precedence-type tests for testing the hypothesis that two distribution functions are equal, which is an extension of the precedence life-test rst proposed by Nelson (1963), when the two samples are progressively Type-II censored. The null distributions of the test statistics are derived. Critical values for some combination of sample sizes and censoring schemes for the proposed tests are presented. Then, we present the exact power functions under the Lehmann alternative, and compare the exact power as well as simulated power (under location-shift) of the proposed precedence test based on nonparametric estimates of CDF with other precedence-type tests. We then examine the power properties of the proposed test procedures through Monte Carlo simulations. Two examples are presented to illustrate all the test procedures discussed here. Finally, we make some concluding remarks.Precedence test; Product-limit estimator; Type-II progressive censoring; Life-testing; level of significance; power; Lehmann alternative; Monte Carlo simulations
Generalizations of the Familywise Error Rate
Consider the problem of simultaneously testing null hypotheses H_1,...,H_s.
The usual approach to dealing with the multiplicity problem is to restrict
attention to procedures that control the familywise error rate (FWER), the
probability of even one false rejection. In many applications, particularly if
s is large, one might be willing to tolerate more than one false rejection
provided the number of such cases is controlled, thereby increasing the ability
of the procedure to detect false null hypotheses. This suggests replacing
control of the FWER by controlling the probability of k or more false
rejections, which we call the k-FWER. We derive both single-step and stepdown
procedures that control the k-FWER, without making any assumptions concerning
the dependence structure of the p-values of the individual tests. In
particular, we derive a stepdown procedure that is quite simple to apply, and
prove that it cannot be improved without violation of control of the k-FWER. We
also consider the false discovery proportion (FDP) defined by the number of
false rejections divided by the total number of rejections (defined to be 0 if
there are no rejections). The false discovery rate proposed by Benjamini and
Hochberg [J. Roy. Statist. Soc. Ser. B 57 (1995) 289-300] controls E(FDP).
Here, we construct methods such that, for any \gamma and \alpha,
P{FDP>\gamma}\le\alpha. Two stepdown methods are proposed. The first holds
under mild conditions on the dependence structure of p-values, while the second
is more conservative but holds without any dependence assumptions.Comment: Published at http://dx.doi.org/10.1214/009053605000000084 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Diffractive charged meson pair production
We investigate the possibility to measure the nonforward gluon distribution
function by means of diffractively produced \pi^+\pi^- and K^+K^- pairs in
polarized lepton nucleon scattering. The resulting cross sections are small and
are dominated by the gluonic contribution. We find relatively large spin
asymmetries, both for \pi^+\pi^- and for K^+K^- pairs.Comment: 15 pages, version with changed kinematical cuts, to be pubished in
Phys.Lett.
Remarks on Adjoint QCD with k Flavors, k>= 2
I summarize what we know of adjoint QCD. Some observations (albeit very
simple) are new.Comment: 12 p. 3 figs; v2: a comment and 2 references adde
Fisher zeros in the Kallen-Lehmann approach to 3D Ising model
The distribution of the Fisher zeros in the Kallen-Lehmann approach to
three-dimensional Ising model is studied. It is argued that the presence of a
non-trivial angle (a cusp) in the distribution of zeros in the complex
temperatures plane near the physical singularity is realized through a strong
breaking of the 2D Ising self-duality. Remarkably, the realization of the cusp
in the Fisher distribution ultimately leads to an improvement of the results of
the Kallen-Lehmann ansatz. In fact, excellent agreement with Monte Carlo
predictions both at high and at low temperatures is observed. Besides,
agreement between both approaches is found for the predictions of the critical
exponent alpha and of the universal amplitude ratio Delta = A_+/A_-, within the
3.5% and 7% of the Monte Carlo predictions, respectively.Comment: 18 pages, 1 figur
Bias in the temperature of helium nanodroplets measured by an embedded rotor
The ro--vibrational spectra of molecules dissolved in liquid He
nanodroplets display rotational structure. Where resolved, this structure has
been used to determine a temperature that has been assumed to equal that of the
intrinsic excitations of the helium droplets containing the molecules.
Consideration of the density of states as a function of energy and total
angular momentum demonstrates that there is a small but significant bias of the
rotor populations that make the temperature extracted from a fit to its
rotational level populations slightly higher than the temperature of the
ripplons of the droplet. This bias grows with both the total angular momentum
of the droplet and with the moment of inertia of the solute molecule.Comment: 6 pages, 1 figure, to be published in Journal of Chemical Physic
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