2,820 research outputs found
Interacting Fermion Systems from Two Dimensional QCD
We consider two dimensional U(N) QCD on the cylinder with a timelike Wilson
line in an arbitrary representation. We show that the theory is equivalent to N
fermions with internal degrees of freedom which interact among themselves with
a generalized Sutherland-type interaction. By evaluating the expectation value
of the Wilson line in the original theory we explicitly find the spectrum and
degeneracies of these particle systems.Comment: 11 pages, UVA-93-11, CERN-TH-6994/9
Modulation of social behavior by the agouti pigmentation gene
Agouti is a secreted neuropeptide that acts as an endogenous antagonist of melanocortin receptors. Mice and rats lacking agouti (called non-agouti) have dark fur due to a disinhibition of melanocortin signaling and pigment deposition in the hair follicle. Non-agouti animals have also been reported to exhibit altered behavior, despite no evidence for the expression of agouti outside the skin. Here we confirm that non-agouti mice show altered social behavior and uncover expression of agouti in the preputial gland, a sebaceous organ in the urinary tract that secretes molecules involved in social behavior. Non-agouti mice had enlarged preputial glands and altered levels of putative preputial pheromones and surgical removal of the gland reversed the behavioral phenotype. These findings demonstrate the existence of an autologous, out-of-skin pathway for the modulation of social behavio
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
Using SU(3) symmetry to constrain the pion BB' couplings, assuming SU(3)
breaking comes only from one-loop pion cloud contributions, and using the the
covariant spectator theory to describe the photon coupling to the quark core,
we show how the experimental masses and magnetic moments of the baryon octet
can be used to set a model independent constraint on the strength of the pion
cloud contributions to the octet, and hence the nucleon, form factors at Q2=0.Comment: 7 pages, 1 figur
Shot Noise in Digital Holography
We discuss on noise in heterodyne holography in an off-axis configuration. We
show that, for a weak signal, the noise is dominated by the shot noise on the
reference beam. This noise corresponds to an equivalent noise on the signal
beam of one photoelectron per pixel, for the whole sequence of images used to
build the digital hologram
Global strong solution to a nonlinear Dirac type equation in one dimension
This paper studies a class of nonlinear massless Dirac equations in one
dimension, which include the equations for massless Thirring model and massless
Gross-Neveu model. Under the assumptions that the initial data has small charge
and is bounded, the global existence of the strong solution is established. The
decay of the local charge is also proved.Comment: 11pages, submitte
Visualizing thickness-dependent magnetic textures in few-layer
Magnetic ordering in two-dimensional (2D) materials has recently emerged as a
promising platform for data storage, computing, and sensing. To advance these
developments, it is vital to gain a detailed understanding of how the magnetic
order evolves on the nanometer-scale as a function of the number of atomic
layers and applied magnetic field. Here, we image few-layer
using a combined scanning superconducting
quantum interference device and atomic force microscopy probe. Maps of the
material's stray magnetic field as a function of applied magnetic field reveal
its magnetization per layer as well as the thickness-dependent magnetic
texture. Using a micromagnetic model, we correlate measured stray-field
patterns with the underlying magnetization configurations, including labyrinth
domains and skyrmionic bubbles. Comparison between real-space images and
simulations demonstrates that the layer dependence of the material's magnetic
texture is a result of the thickness-dependent balance between crystalline and
shape anisotropy. These findings represent an important step towards 2D
spintronic devices with engineered spin configurations and controlled
dependence on external magnetic fields.Comment: 15 pages, 4 figures, and supplementary informatio
The Correlation and Accuracy of Glucose Levels between Interstitial Fluid and Venous Plasma by Continuous Glucose Monitoring System
Willingness to participate in future HIV prevention studies among gay and bisexual men in Scotland, UK: a challenge for intervention trials
This article examines willingness to participate in future HIV prevention research among gay and bisexual men in Scotland, UK. Anonymous, self-complete questionnaires and Orasure Gäó oral fluid samples were collected in commercial gay venues. 1,320 men were eligible for inclusion. 78.2% reported willingness to participate in future HIV prevention research; 64.6% for an HIV vaccine, 57.4% for a behaviour change study, and 53.0% for a rectal microbicide. In multivariate analysis, for HIV vaccine research, greater age, minority ethnicity, and not providing an oral fluid sample were associated with lower willingness; heterosexual orientation and not providing an oral fluid sample were for microbicides; higher education and greater HIV treatment optimism were for behaviour change. STI testing remained associated with being more willing to participate in microbicide research and frequent gay scene use remained associated with being more willing to participate in behaviour change research. Having an STI in the past 12 months remained significantly associated with being willing to participate in all three study types. There were no associations between sexual risk behaviour and willingness. Although most men expressed willingness to participate in future research, recruitment of high-risk men, who have the potential to benefit most, is likely to be more challenging
Microscopic observation of magnon bound states and their dynamics
More than eighty years ago, H. Bethe pointed out the existence of bound
states of elementary spin waves in one-dimensional quantum magnets. To date,
identifying signatures of such magnon bound states has remained a subject of
intense theoretical research while their detection has proved challenging for
experiments. Ultracold atoms offer an ideal setting to reveal such bound states
by tracking the spin dynamics after a local quantum quench with single-spin and
single-site resolution. Here we report on the direct observation of two-magnon
bound states using in-situ correlation measurements in a one-dimensional
Heisenberg spin chain realized with ultracold bosonic atoms in an optical
lattice. We observe the quantum walk of free and bound magnon states through
time-resolved measurements of the two spin impurities. The increased effective
mass of the compound magnon state results in slower spin dynamics as compared
to single magnon excitations. In our measurements, we also determine the decay
time of bound magnons, which is most likely limited by scattering on thermal
fluctuations in the system. Our results open a new pathway for studying
fundamental properties of quantum magnets and, more generally, properties of
interacting impurities in quantum many-body systems.Comment: 8 pages, 7 figure
Relic densities including Sommerfeld enhancements in the MSSM
We have developed a general formalism to compute Sommerfeld enhancement (SE)
factors for a multi-state system of fermions, in all possible spin
configurations and with generic long-range interactions. We show how to include
such SE effects in an accurate calculation of the thermal relic density for
WIMP dark matter candidates. We apply the method to the MSSM and perform a
numerical study of the relic abundance of neutralinos with arbitrary
composition and including the SE due to the exchange of the W and Z bosons,
photons and Higgses. We find that the relic density can be suppressed by a
factor of a few in a seizable region of the parameter space, mostly for
Wino-like neutralino with mass of a few TeV, and up to an order of magnitude
close to a resonance.Comment: 23 pages, 7 figures; table 1 corrected and rearranged, numerical
results practically unchanged, matches published versio
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