5,526 research outputs found
Reducible Correlations in Dicke States
We apply a simple observation to show that the generalized Dicke states can
be determined from their reduced subsystems. In this framework, it is
sufficient to calculate the expression for only the diagonal elements of the
reudced density matrices in terms of the state coefficients. We prove that the
correlation in generalized Dicke states can be reduced to
-partite level. Application to the Quantum Marginal Problem is also
discussed.Comment: 12 pages, single column; accepted in J. Phys. A as FT
Implications of \eta' Coupling in the Chiral Constituent Quark Model
Using the latest data pertaining to \bar u-\bar d asymmetry and the spin
polarization functions, detailed implications of the possible values of the
coupling strength of the singlet Goldstone boson \eta' have been investigated
in the \chiCQM with configuration mixing. Using \Delta u, \Delta_3, \bar u-\bar
d and \bar u/\bar d, the possible ranges of the coupling parameters a, \alpha^2
a, \beta^2 a and \zeta^2 a, representing respectively the probabilities of
fluctuations to pions, K, \eta and \eta^{'}, are found. To further constrain
the coupling strength of \eta', detailed fits have been obtained for spin
polarization functions, quark distribution functions and baryon octet magnetic
moments. The fits clearly establish that a small non-zero value of the coupling
of \eta' is preferred over the higher values of as well as when
\zeta=0, the latter implying the absence of \eta' from the dynamics of \chiCQM.
Our best fit achieves an overall excellent fit to the data, in particular for
\Delta u, \Delta d, \Delta_8 as well as the magnetic moments \mu_{n},
\mu_{\Sigma^-}, \mu_{\Sigma^+} and \mu_{\Xi^-}. The implications of \eta' on
the gluon polarization have also been investigated.Comment: 7 pages, 2 tables. Presented at the 17th International Spin Physics
Symposium, Kyoto, Japan, October 2-7, 200
I-surfaces with one T-singularity
We classify normal stable surfaces with KX2=1, pg= 2 and q= 0 with a unique singular point which is a non-canonical T-singularity, thus exhibiting two divisors in the main component and a new irreducible component of the moduli space of stable surfaces M¯ 1 , 3
Chiral constituent quark model and the coupling strength of eta'
Using the latest data pertaining to \bar u-\bar d asymmetry and the spin
polarization functions, detailed implications of the possible values of the
coupling strength of the singlet Goldstone boson \eta' have been investigated
in the \chiCQM with configuration mixing. Using \Delta u, \Delta_3, \bar u-\bar
d and \bar u/\bar d, the possible ranges of the coupling parameters a, \alpha^
2, \beta^ 2 and \zeta^ 2, representing respectively the probabilities of
fluctuations to pions, K, \eta and \eta^{'}, are shown to be 0.10 \lesssim a
\lesssim 0.14, 0.2\lesssim \alpha \lesssim 0.5, 0.2\lesssim \beta \lesssim 0.7
and 0.10 lesssim |\zeta| \lesssim 0.70. To constrain the coupling strength of
\eta', detailed fits have been obtained for spin polarization functions, quark
distribution functions and baryon octet magnetic moments corresponding to the
following sets of parameters: a=0.1, \alpha=0.4, \beta=0.7, |\zeta|=0.65 (Case
I); a=0.1, \alpha=0.4, \beta=0.6, |\zeta|=0.70 (Case II); a=0.14, \alpha=0.4,
\beta=0.2, \zeta=0 (Case III) and a=0.13, \alpha=\beta=0.45, |\zeta|=0.10 (Case
IV). Case I represents the calculations where a is fixed to be 0.1, in
accordance with earlier calculations, whereas other parameters are treated free
and the Case IV represents our best fit. The fits clearly establish that a
small non-zero value of the coupling of \eta' is preferred over the higher
values of \eta' as well as when \zeta=0, the latter implying the absence of
\eta' from the dynamics of \chiCQM. Our best fit achieves an overall excellent
fit to the data, in particular the fit for \Delta u, \Delta d, \Delta_8 as well
as the magnetic moments \mu_{n}, \mu_{\Sigma^-}, \mu_{\Sigma^+} and \mu_{\Xi^-}
is almost perfect, the \mu_{\Xi^-} being a difficult case for most of the
similar calculations.Comment: 8 RevTeX pages, 2 Tables, Revised version to appear in Int.J.Mod.Phys
A condition for first order phase transitions in quantum mechanical tunneling models
A criterion is derived for the determination of parameter domains of first
order phase transitions in quantum mechanical tunneling models. The criterion
is tested by application to various models, in particular to some which have
been used recently to explore spin tunneling in macroscopic particles. In each
case agreement is found with previously heuristically determined domains.Comment: 13 pages, 5 figure
Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier Relaxation and Recombination Dynamics in Epitaxial Graphene
The ultrafast relaxation and recombination dynamics of photogenerated
electrons and holes in epitaxial graphene are studied using optical-pump
Terahertz-probe spectroscopy. The conductivity in graphene at Terahertz
frequencies depends on the carrier concentration as well as the carrier
distribution in energy. Time-resolved studies of the conductivity can therefore
be used to probe the dynamics associated with carrier intraband relaxation and
interband recombination. We report the electron-hole recombination times in
epitaxial graphene for the first time. Our results show that carrier cooling
occurs on sub-picosecond time scales and that interband recombination times are
carrier density dependent.Comment: 4 pages, 5 figure
Sharp change over from compound nuclear fission to shape dependent quasi fission
Fission fragment mass distribution has been measured from the decay of
Bk nucleus populating via two entrance channels with slight difference
in mass asymmetries but belonging on either side of the Businaro Gallone mass
asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb
barrier, at similar excitation energies the width of the fission fragment mass
distribution was found to be drastically different for the N +
Th reaction compared to the B + U reaction. The entrance
channel mass asymmetry was found to affect the fusion process sharply.Comment: 4 pages,6 figure
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