143,160 research outputs found
Cuprates as doped U(1) spin liquids
We explore theoretically the notion that the underdoped cuprates may be
viewed as doped U(1) spin liquid Mott insulators. We pursue a conceptually
clear version of this idea that naturally incorporates several aspects of the
phenomenology of the cuprates. We argue that the low doping region may be
fruitfully discussed in terms of the universal physics associated with a
chemical potential tuned Mott transition between a U(1) spin liquid insulator
and a d-wave superconductor. A precise characterization of the deconfinement in
the U(1) spin liquid is provided by the emergence of a conserved gauge flux.
This extra conservation law should hold at least approximately in the
underdoped materials. Experiments that could possibly detect this conserved
gauge flux are proposed.Comment: 11 pages, 7 figure
Universality in a Class of Q-Ball Solutions: An Analytic Approach
The properties of Q-balls in the general case of a sixth order potential have
been studied using analytic methods. In particular, for a given potential, the
initial field value that leads to the soliton solution has been derived and the
corresponding energy and charge have been explicitly evaluated. The proposed
scheme is found to work reasonably well for all allowed values of the model
parameters.Comment: 9 Pages, 6 Figure
The vibrational predissociation spectroscopy of hydrogen cluster ions
The first infrared spectra of protonated hydrogen clusters in the gas phase have been observed. Predissociation spectra were taken with a tandem mass spectrometer: mass selected hydrogen cluster ions were irradiated inside a rf ion trap by a tunable infrared laser, and the fragment ions created by photodissociation of the clusters were mass selected and detected. Spectra for each product channel were measured by counting fragment ions as a function of laser frequency. Low resolution spectra (Deltanu=10 cm^−1) in the region from 3800 to 4200 cm^−1 were observed for the ions H + 5, H + 7, and H + 9 at 3910, 3980, and 4020 cm−1, respectively. A band was also observed for H + 5 at 3532 cm^−1. No rotational structure was resolved. The frequencies of the band maxima agree well with the frequencies predicted by previous ab initio calculations for the highest modes
Electromagnetic production of vector mesons at low energies
We have investigated exclusive photoproduction of light vector mesons
(, and ) on the nucleon at low energies. In order to
explore the questions concerning the so-called missing nucleon resonances, we
first establish the predictions from a model based on the Pomeron and meson
exchange mechanisms. We have also explored the contributions due to the
mechanisms involving - and -channel intermediate nucleon state. Some
discrepancies found at the energies near threshold and large scattering angles
suggest a possibility of using this reaction to identify the nucleon
resonances.Comment: 9 pages, LaTeX with sprocl.sty, 5 figures (11 eps files), Talk
presented at the NSTAR2000 Workshop, The Physics of Excited Nucleons,
Jefferson Lab., Newport News, Feb. 16-19, 200
Higher and missing resonances in omega photoproduction
We study the role of the nucleon resonances () in
photoproduction by using the quark model resonance parameters predicted by
Capstick and Roberts. The employed and
amplitudes include the configuration mixing effects due to the residual
quark-quark interactions. The contributions from the nucleon resonances are
found to be important in the differential cross sections at large scattering
angles and various spin observables. In particular, the parity asymmetry and
beam-target double asymmetry at forward scattering angles are suggested for a
crucial test of our predictions. The dominant contributions are found to be
from , a missing resonance, and which is
identified as the of the Particle Data Group.Comment: 8 pages, LaTeX with ws-p8-50x6-00.cls, 4 figures (5 eps files), Talk
presented at the NSTAR2001 Workshop on the Physics of Excited Nucleons,
Mainz, Germany, Mar. 7-10, 200
Closing a Loophole in Factorization Proofs
We address the possibility in factorization proofs that low-energy collinear
gluons can couple to soft gluons.Comment: 3 pages, 5 figures, contribution to the proceedings of Quark
Confinement and the Hadron Spectrum I
Rate of Convergence in Nonlinear Hartree Dynamics with Factorized Initial Data
The mean field dynamics of an -particle weekly interacting Boson system
can be described by the nonlinear Hartree equation. In this paper, we present
estimates on the 1/N rate of convergence of many-body Schr\"{o}dinger dynamics
to the one-body nonlinear Hartree dynamics with factorized initial data with
two-body interaction potential in .Comment: AMS LaTex, 21 page
Branching process approach for Boolean bipartite networks of metabolic reactions
The branching process (BP) approach has been successful in explaining the
avalanche dynamics in complex networks. However, its applications are mainly
focused on unipartite networks, in which all nodes are of the same type. Here,
motivated by a need to understand avalanche dynamics in metabolic networks, we
extend the BP approach to a particular bipartite network composed of Boolean
AND and OR logic gates. We reduce the bipartite network into a unipartite
network by integrating out OR gates, and obtain the effective branching ratio
for the remaining AND gates. Then the standard BP approach is applied to the
reduced network, and the avalanche size distribution is obtained. We test the
BP results with simulations on the model networks and two microbial metabolic
networks, demonstrating the usefulness of the BP approach
- …