228 research outputs found
Baryon Fields with U_L(3) \times U_R(3) Chiral Symmetry: Axial Currents of Nucleons and Hyperons
We use the conventional F and D octet and decimet generator matrices to
reformulate chiral properties of local (non-derivative) and one-derivative
non-local fields of baryons consisting of three quarks with flavor SU(3)
symmetry that were expressed in SU(3) tensor form in Ref. [12]. We show
explicitly the chiral transformations of the [(6,3)\oplus(3,6)] chiral
multiplet in the "SU(3) particle basis", for the first time to our knowledge,
as well as those of the (3,\bar{3}) \oplus (\bar{3}, 3), (8,1) \oplus (1,8)
multiplets, which have been recorded before in Refs. [4,5]. We derive the
vector and axial-vector Noether currents, and show explicitly that their zeroth
(charge-like) components close the SU_L(3) \times SU_R(3) chiral algebra. We
use these results to study the effects of mixing of (three-quark) chiral
multiplets on the axial current matrix elements of hyperons and nucleons. We
show, in particular, that there is a strong correlation, indeed a definite
relation between the flavor-singlet (i.e. the zeroth), the isovector (the
third) and the eighth flavor component of the axial current, which is in decent
agreement with the measured ones.Comment: one typo correction, and accepted by PR
WKB approximation for multi-channel barrier penetrability
Using a method of local transmission matrix, we generalize the well-known WKB
formula for a barrier penetrability to multi-channel systems. We compare the
WKB penetrability with a solution of the coupled-channels equations, and show
that the WKB formula works well at energies well below the lowest adiabatic
barrier. We also discuss the eigen-channel approach to a multi-channel
tunneling, which may improve the performance of the WKB formula near and above
the barrier.Comment: 15 pages, 4 eps figure
Wave Mechanics of a Two Wire Atomic Beamsplitter
We consider the problem of an atomic beam propagating quantum mechanically
through an atom beam splitter. Casting the problem in an adiabatic
representation (in the spirit of the Born-Oppenheimer approximation in
molecular physics) sheds light on explicit effects due to non-adiabatic passage
of the atoms through the splitter region. We are thus able to probe the fully
three dimensional structure of the beam splitter, gathering quantitative
information about mode-mixing, splitting ratios,and reflection and transmission
probabilities
A comparative study of some models of incoherence at the mesoscopic scale
The pre-existing literature on phenomena at the mesoscopic scale is concerned
among other things with phase coherent transport. Phase coherent transport
dominates at very low temperatures. With increase in temperature, as the system
size becomes comparable to the inelastic mean free path phase incoherence sets
in. This incoherence further leads to dephasing, and as a consequence purely
quantum effects in electron transport give way to classical macroscopic
behavior. In this work we consider two distinct phenomenological models of
incoherent transport, the Coherent Absorption and Wave Attenuation models. We
reveal some physical problems in the Coherent Absorption model as opposed to
the Wave Attenuation model. We also compare our proposed model with experiments
in case of the much studied peak to valley ratios in resonant tunneling diodes,
magneto-conductance oscillations and Fano resonances in case of Aharonov-Bohm
rings.Comment: 20 pages, 9 figure
Time-dependent approach to many-particle tunneling in one-dimension
Employing the time-dependent approach, we investigate a quantum tunneling
decay of many-particle systems. We apply it to a one-dimensional three-body
problem with a heavy core nucleus and two valence protons. We calculate the
decay width for two-proton emission from the survival probability, which well
obeys the exponential decay-law after a sufficient time. The effect of the
correlation between the two emitted protons is also studied by observing the
time evolution of the two-particle density distribution. It is shown that the
pairing correlation significantly enhances the probability for the simultaneous
diproton decay.Comment: 9 pages, 10 eps figure
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