234,026 research outputs found
Mass Spectrum and Bounds on the Couplings in Yukawa Models With Mirror-Fermions
The symmetric Yukawa model with mirror-fermions
in the limit where the mirror-fermion is decoupled is studied both analytically
and numerically. The bare scalar self-coupling is fixed at zero and
infinity. The phase structure is explored and the relevant phase transition is
found to be consistent with a second order one. The fermionic mass spectrum
close to that transition is discussed and a first non-perturbative estimate of
the influence of fermions on the upper and lower bounds on the renormalized
scalar self-coupling is given. Numerical results are confronted with
perturbative predictions.Comment: 7 (Latex) page
Pentaquarks
Since LEPS collaboration reported the first evidence of pentaquark
in early 2003, eleven other experimental groups have confirmed this exotic
state while many other groups didn't see any signal. If this state is further
established by future high statistical experiments, its discovery shall be one
of the most important events in hadron physics for the past three decades. This
exotic baryon with such a low mass and so narrow a width imposes a big
challenge to hadron theorists. Up to now, there have appeared more than two
hundred theoretical papers trying to interpret this charming state. I will
review some important theoretical developments on pentaquarks based on my
biased personal views.Comment: Review Commissioned by International Journal of Modern Physics
Fluctuation-induced tunneling conduction through RuO nanowire contacts
A good understanding of the electronic conduction processes through
nanocontacts is a crucial step for the implementation of functional
nanoelectronic devices. We have studied the current-voltage (-)
characteristics of nanocontacts between single metallic RuO nanowires (NWs)
and contacting Au electrodes which were pre-patterned by simple
photolithography. Both the temperature behavior of contact resistance in the
low-bias voltage ohmic regime and the - curves in the high-bias voltage
non-ohmic regime have been investigated. We found that the electronic
conduction processes in the wide temperature interval 1--300 K can be well
described by the fluctuation-induced tunneling (FIT) conduction theory. Taken
together with our previous work (Lin {\it et al.}, Nanotechnology {\bf 19},
365201 (2008)) where the nanocontacts were fabricated by delicate electron-beam
lithography, our study demonstrates the general validity of the FIT model in
characterizing electronic nanocontacts.Comment: 6 pages, 5 figure
Exciton Hierarchies in Gapped Carbon Nanotubes
We present evidence that the strong electron-electron interactions in gapped
carbon nanotubes lead to finite hierarchies of excitons within a given nanotube
subband. We study these hierarchies by employing a field theoretic reduction of
the gapped carbon nanotube permitting electron-electron interactions to be
treated exactly. We analyze this reduction by employing a Wilsonian-like
numerical renormalization group. We are so able to determine the gap ratios of
the one-photon excitons as a function of the effective strength of
interactions. We also determine within the same subband the gaps of the
two-photon excitons, the single particle gaps, as well as a subset of the dark
excitons. The strong electron-electron interactions in addition lead to
strongly renormalized dispersion relations where the consequences of
spin-charge separation can be readily observed.Comment: 8 pages, 4 figure
Two-dimensional turbulence models
Two-dimensional turbulence models are compared with experimental measurements made using an array of instrumented towers. The spatial correlation coefficient, the two-point spectrum or cross spectrum, and the coherence function are discussed. The prediction techniques in general agree reasonably well with the experimental results. Measurements of the integral length scale however, do not correlate well with the prediction model
Effective hadronic Lagrangian for charm mesons
An effective hadronic Lagrangian including the charm mesons is introduced to
study their interactions in hadronic matter. Using coupling constants that are
determined either empirically or by the SU(4) symmetry, we have evaluated the
absorption cross sections of and the scattering cross sections of
and by and mesons.Comment: 5 pages, 4 eps figures, presented at Strangeness 2000, Berkeley. Uses
iopart.cl
Path Integral Solution by Sum Over Perturbation Series
A method for calculating the relativistic path integral solution via sum over
perturbation series is given. As an application the exact path integral
solution of the relativistic Aharonov-Bohm-Coulomb system is obtained by the
method. Different from the earlier treatment based on the space-time
transformation and infinite multiple-valued trasformation of
Kustaanheimo-Stiefel in order to perform path integral, the method developed in
this contribution involves only the explicit form of a simple Green's function
and an explicit path integral is avoided.Comment: 13 pages, ReVTeX, no figure
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