296,808 research outputs found

### Coherence and pairing in a doped Mott insulator: Application to the cuprates

The issues of single particle coherence and its interplay with singlet
pairing are studied within the slave boson gauge theory of a doped Mott
insulator. Prior work by one of us (T. Senthil, arXiv:0804.1555) showed that
the coherence scale below which Landau quasiparticles emerge is parametrically
lower than that identified in the slave boson mean field theory. Here we study
the resulting new non-fermi liquid intermediate temperature regime
characterized by a single particle scattering rate that is linear in
temperature ($T$). In the presence of a d-wave pair amplitude this leads to a
pseudogap state with $T$ dependent Fermi arcs near the nodal direction.
Implications for understanding the cuprates are discussed.Comment: 4+ pages, 1 figure. Sequel to arXiv:0903.087

### Direct transmission of pictorial information in multimode optical fibers

The problem of coherent image transmission through a single multimode optical fiber is discussed. A scheme is presented for recovering the transmitted image after distortions brought about by the fiber modes dispersion. Realization of this scheme by holographic techniques and with lens systems is proposed, and its limitations pointed out. The application of this scheme in canceling out temporal signal dispersion in a multimode fiber transmission line is also discussed briefly

### Susceptibility of a spinon Fermi surface coupled to a U(1) gauge field

We study the theory of a U(1) gauge field coupled to a spinon Fermi surface.
Recently this model has been proposed as a possible description of the organic
compound $\kappa-(BEDT-TTF)_2 Cu_2 (CN)_3$. We calculate the susceptibility of
this system and in particular examine the effect of pairing of the underlying
spin liquid. We show that this proposed theory is consistent with the observed
susceptibility measurements.Comment: 5 pages, 4 figure

### U(1) Gauge Theory of the Hubbard Model : Spin Liquid States and Possible Application to k-(BEDT-TTF)_2 Cu_2 (CN)_3

We formulate a U(1) gauge theory of the Hubbard model in the slave-rotor
representation. From this formalism it is argued that spin liquid phases may
exist near the Mott transition in the Hubbard model on triangular and honeycomb
lattices at half filling. The organic compound k-(BEDT-TTF)_2 Cu_2 (CN)_3 is a
good candidate for the spin liquid state on a triangular lattice. We predict a
highly unusual temperature dependence for the thermal conductivity of this
material.Comment: 5 pages, 2 figures; paper shortened and the phase diagram of
anisotropic triangular lattice correcte

### Intensity correlations in electronic wave propagation in a disordered medium: the influence of spin-orbit scattering

We obtain explicit expressions for the correlation functions of transmission
and reflection coefficients of coherent electronic waves propagating through a
disordered quasi-one-dimensional medium with purely elastic diffusive
scattering in the presence of spin-orbit interactions. We find in the metallic
regime both large local intensity fluctuations and long-range correlations
which ultimately lead to universal conductance fluctuations. We show that the
main effect of spin-orbit scattering is to suppress both local and long-range
intensity fluctuations by a universal symmetry factor 4. We use a scattering
approach based on random transfer matrices.Comment: 15 pages, written in plain TeX, Preprint OUTP-93-42S (University of
Oxford), to appear in Phys. Rev.

### Hole correlation and antiferromagnetic order in the t-J model

We study the t-J model with four holes on a 32-site square lattice using
exact diagonalization. This system corresponds to doping level x=1/8. At the
``realistic'' parameter J/t=0.3, holes in the ground state of this system are
unbound. They have short range repulsion due to lowering of kinetic energy.
There is no antiferromagnetic spin order and the electron momentum distribution
function resembles hole pockets. Furthermore, we show evidence that in case
antiferromagnetic order exists, holes form d-wave bound pairs and there is
mutual repulsion among hole pairs. This presumably will occur at low doping
level. This scenario is compatible with a checkerboard-type charge density
state proposed to explain the ``1/8 anomaly'' in the LSCO family, except that
it is the ground state only when the system possesses strong antiferromagnetic
order

### Persistence in systems with algebraic interaction

Persistence in coarsening 1D spin systems with a power law interaction
$r^{-1-\sigma}$ is considered. Numerical studies indicate that for sufficiently
large values of the interaction exponent $\sigma$ ($\sigma\geq 1/2$ in our
simulations), persistence decays as an algebraic function of the length scale
$L$, $P(L)\sim L^{-\theta}$. The Persistence exponent $\theta$ is found to be
independent on the force exponent $\sigma$ and close to its value for the
extremal ($\sigma \to \infty$) model, $\bar\theta=0.17507588...$. For smaller
values of the force exponent ($\sigma< 1/2$), finite size effects prevent the
system from reaching the asymptotic regime. Scaling arguments suggest that in
order to avoid significant boundary effects for small $\sigma$, the system size
should grow as ${[{\cal O}(1/\sigma)]}^{1/\sigma}$.Comment: 4 pages 4 figure

### Double-heterostructure GaAs-GaAIAs injection lasers on semi-insulating substrates using carrier crowding

GaAsâGaAlAs doubleâheterostructure lasers were fabricated on semiâinsulating substrates. Laser action based on carrier confinement via the crowding effect has been demonstrated. Laser action takes place in a narrow (10â20 ÎŒm) region near the edge of the mesa where the current is injected. The threshold current is low and is comparable to that of stripeâgeometry lasers

### A Possible Origin of Dark Energy

We discuss the possibility that the existence of dark energy may be due to
the presence of a spin zero field $\phi(x)$, either elementary or composite. In
the presence of other matter field, the transformation $\phi(x)\to \phi(x) +$
constant can generate a negative pressure, like the cosmological constant. In
this picture, our universe can be thought as a very large bag, similar to the
much smaller MIT bag model for a single nucleon.Comment: 4 pages, no figure, typos correcte

### Measuring Perceived Effects of Drinking an Extract of Basidiomycetes Agaricus Blazei Murill: A Survey of Japanese Consumers with Cancer

BACKGROUND. To survey cancer patients who consume an extract of the Basidiomycetes Agaricus blazei Murill mushroom (Sen-Sei-Ro) to measure their self-assessment of its effects and to develop an instrument for use in future randomized trials. METHODS. We designed, translated and mailed a survey to 2,346 Japanese consumers of Sen-Sei-Ro self-designated as cancer patients. The survey assessed consumer demographics, cancer history, Sen-Sei-Ro consumption, and its perceived effects. We performed exploratory psychometric analyses to identify distinct, multi-item scales that could summarize perceptions of effects. RESULTS. We received completed questionnaires from 782 (33%) of the sampled Sen-Sei-Ro consumers with a cancer history. Respondents represented a broad range of cancer patients familiar with Sen-Sei-Ro. Nearly all had begun consumption after their cancer diagnosis. These consumers expressed consistently positive views, though not extremely so, with more benefit reported for more abstract benefits such as emotional and physical well-being than relief of specific symptoms. We identified two conceptually and empirically distinct and internally consistent summary scales measuring Sen-Sei-Ro consumers' perceptions of its effects, Relief of Symptoms and Functional Well-being (Cronbach's alpha: Relief of Symptoms, Î± = .74; Functional Well-Being, Î± = .91). CONCLUSION. Respondents to our survey of Sen-Sei-Ro consumers with cancer reported favorable perceived effects from its use. Our instrument, when further validated, may be a useful outcome in trials assessing this and other complementary and alternative medicine (CAM) substances in cancer patients.Kyowa-S.S.I., Tokyo, Japa

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