29,139 research outputs found
A Simple Method for Computing the Non-Linear Mass Correlation Function with Implications for Stable Clustering
We propose a simple and accurate method for computing analytically the mass
correlation function for cold dark matter and scale-free models that fits
N-body simulations over a range that extends from the linear to the strongly
non-linear regime. The method, based on the dynamical evolution of the pair
conservation equation, relies on a universal relation between the pair-wise
velocity and the smoothed correlation function valid for high and low density
models, as derived empirically from N-body simulations. An intriguing
alternative relation, based on the stable-clustering hypothesis, predicts a
power-law behavior of the mass correlation function that disagrees with N-body
simulations but conforms well to the observed galaxy correlation function if
negligible bias is assumed. The method is a useful tool for rapidly exploring a
wide span of models and, at the same time, raises new questions about large
scale structure formation.Comment: 10 pages, 3 figure
Band Structure of the Fractional Quantum Hall Effect
The eigenstates of interacting electrons in the fractional quantum Hall phase
typically form fairly well defined bands in the energy space. We show that the
composite fermion theory gives insight into the origin of these bands and
provides an accurate and complete microscopic description of the strongly
correlated many-body states in the low-energy bands. Thus, somewhat like in
Landau's fermi liquid theory, there is a one-to-one correspondence between the
low energy Hilbert space of strongly interacting electrons in the fractinal
quantum Hall regime and that of weakly interacting electrons in the integer
quantum Hall regime.Comment: 10 page
The relation between the two-point and the three-point correlation functions in the non-linear gravitational clustering regime
The connection between the two-point and the three-point correlation
functions in the non-linear gravitational clustering regime is studied. Under a
scaling hypothesis, we find that the three-point correlation function, ,
obeys the scaling law in the
nonlinear regime, where , , , and are the two-point
correlation function, the power index of the power spectrum in the nonlinear
regime, the number of spatial dimensions, and the power index of the phase
correlations, respectively. The new formula reveals the origin of the power
index of the three-point correlation function. We also obtain the theoretical
condition for which the ``hierarchical form'' is
reproduced.Comment: 16 pages, 4 figures. Accepted for publication in APJ. Some sentences
and figures are revise
Depression among Adolescent Students in a Rural Block of Haryana: A Cross Sectional Study
Background: Depression among adolescent is an area of increasing concern worldwide. This study aimed to assess the prevalence of depression among school going adolescents in government and private schools in a rural area of block Beri of Haryana. Methods: A cross sectional study was conducted in a sample size of 600 students (300 males and 300 females) studying in class 8th to 12th. A pre designed, pre tested tool SCL 90 R containing 90 items was used to screen depression in these students. Depression is one of the psychiatric morbidity screened by this tool. Cut off point of estimated raw score of 1 was used to label as depression. All the statistical analysis was carried out using SPSS 20. Results: The overall prevalence of depression was found to be 39.1% with mild depression to be 33.1% and moderate to severe depression to be 6%. Depression was significantly more among female students (45%) than male students (33.3%). Overall prevalence of depression significantly increased with age. It was found to be 34.3% among 13-14 years age-group, 41% among 15-16 years age-group and 57.1% among 17-19 years age-group. The association of depression with other socio demographic profile like socio economic status, literacy level of mother and father, employment status of mother was found to be non-significant. Conclusion: It is concluded from the present study that more than one – third (39%) of school adolescents suffered from depression. Reasons for such high prevalence of depression need to be determined. At the same time teachers and parents should be made aware of this problem and appropriate counselling of students should be done through regular school-based screening programme.
One-Dimensional Theory of the Quantum Hall System
We consider the lowest Landau level on a torus as a function of its
circumference . When , the ground state at general rational
filling fraction is a crystal with a gap--a Tao-Thouless state. For filling
fractions , these states are the limits of Laughlin's or Jain's
wave functions describing the gapped quantum Hall states when .
For the half-filled Landau level, there is a transition to a Fermi sea of
non-interacting neutral dipoles, or rather to a Luttinger liquid modification
thereof, at magnetic lengths. This state is a version of the
Rezayi-Read state, and develops continuously into the state that is believed to
describe the observed metallic phase as . Furthermore, the
effective Landau level structure that emerges within the lowest Landau level
follows from the magnetic symmetries.Comment: 4 pages, 1 figur
Dynamics of pairwise motions
We derive a simple closed-form expression, relating \vs(r) -- the mean
relative velocity of pairs of galaxies at fixed separation -- to the
two-point correlation function of mass density fluctuations, . We
compare our analytic model for \vs(r) with N-body simulations, and find
excellent agreement in the entire dynamical range probed by the simulations
(0.1 \lsim \xi \lsim 1000). Our results can be used to estimate the
cosmological density parameter, \Om, directly from redshift-distance surveys,
like Mark III.Comment: 10 pages 2 Figs., submitted to ApJ Let
Projectile Excitations in Reactions
It has recently been proven from measurements of the spin-transfer
coefficients and that there is a small but non-vanishing
component , in the inclusive reaction
cross section . It is shown that the dominant part of the measured
can be explained in terms of the projectile excitation
mechanism. An estimate is further made of contributions to from
s-wave rescattering process. It is found that s-wave rescattering contribution
is much smaller than the contribution coming from projectile
excitation mechanism. The addition of s-wave rescattering contribution to the
dominant part, however, improves the fit to the data.Comment: 9 pages, Revtex, figures can be obtained upon reques
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