110,597 research outputs found
Orbitally excited and hybrid mesons from the lattice
We discuss in general the construction of gauge-invariant non-local meson
operators on the lattice. We use such operators to study the - and -wave
mesons as well as hybrid mesons in quenched QCD, with quark masses near the
strange quark mass. The resulting spectra are compared with experiment for the
orbital excitations. For the states produced by gluonic excitations (hybrid
mesons) we find evidence of mixing for non-exotic quantum numbers. We give
predictions for masses of the spin-exotic hybrid mesons with $J^{PC}=1^{-+},\
0^{+-}2^{+-}$.Comment: 31 pages, LATEX, 8 postscript figures. Reference adde
The Partially-Split Hall Bar: Tunneling in the Bosonic Integer Quantum Hall Effect
We study point-contact tunneling in the integer quantum Hall state of bosons.
This symmetry-protected topological state has electrical Hall conductivity
equal to and vanishing thermal Hall conductivity. In contrast to the
integer quantum Hall state of fermions, a point contact can have a dramatic
effect on the low energy physics. In the absence of disorder, a point contact
generically leads to a partially-split Hall bar geometry. We describe the
resulting intermediate fixed point via the two-terminal electrical (Hall)
conductance of the edge modes. Disorder along the edge, however, both restores
the universality of the two-terminal conductance and helps preserve the
integrity of the Hall bar within the relevant parameter regime.Comment: 12 pages, 5 figures; v.2: typos fixed and clarified some argument
Quantum metrology and its application in biology
Quantum metrology provides a route to overcome practical limits in sensing
devices. It holds particular relevance to biology, where sensitivity and
resolution constraints restrict applications both in fundamental biophysics and
in medicine. Here, we review quantum metrology from this biological context,
focusing on optical techniques due to their particular relevance for biological
imaging, sensing, and stimulation. Our understanding of quantum mechanics has
already enabled important applications in biology, including positron emission
tomography (PET) with entangled photons, magnetic resonance imaging (MRI) using
nuclear magnetic resonance, and bio-magnetic imaging with superconducting
quantum interference devices (SQUIDs). In quantum metrology an even greater
range of applications arise from the ability to not just understand, but to
engineer, coherence and correlations at the quantum level. In the past few
years, quite dramatic progress has been seen in applying these ideas into
biological systems. Capabilities that have been demonstrated include enhanced
sensitivity and resolution, immunity to imaging artifacts and technical noise,
and characterization of the biological response to light at the single-photon
level. New quantum measurement techniques offer even greater promise, raising
the prospect for improved multi-photon microscopy and magnetic imaging, among
many other possible applications. Realization of this potential will require
cross-disciplinary input from researchers in both biology and quantum physics.
In this review we seek to communicate the developments of quantum metrology in
a way that is accessible to biologists and biophysicists, while providing
sufficient detail to allow the interested reader to obtain a solid
understanding of the field. We further seek to introduce quantum physicists to
some of the central challenges of optical measurements in biological science.Comment: Submitted review article, comments and suggestions welcom
The Culturally-adapted Early Pathways Program for Young Latino Children in Poverty: A Randomized Controlled Trial
This study used a randomized controlled design with treatment and wait-list conditions to evaluate the efficacy of a culturally adapted version of the Early Pathways program (EP; Fox & Gresl, 2014), an in-home, parent–child therapy program with 137 at-risk Latino children under the age of 6 referred for severe behavior and emotional problems, such as aggression, oppositional behavior, self-injury, and property destruction. EP directly engaged the parent–child dyad, emphasizing parent-directed training, child-led play, psychoeducation, and cognitive–behavioral strategies. Cultural modifications included establishing community partnerships to identify Latino family needs, translation of materials, offering bilingual services, acculturation assessment, and cultural competence training. Multivariate analyses of covariance (MANCOVA) revealed significant differences between the immediate and delayed treatment groups on all posttest measures with the pretest scores as covariates. After the delayed group completed treatment, repeated measures, multivariate analyses of variance (MANOVA) showed significant improvement for both groups on all measures with maintenance at 4- to 6-week follow-up. Outcomes included reduced child behavior problems, increased child prosocial behaviors, improved caregiver limit setting, enhanced caregiver nurturing, improved parent–child relationships, and a decrease in clinical diagnoses following treatment. This study highlights the efficacy of using culturally adapted early intervention services for young Latino children in poverty referred for significant behavior and emotional problems
Understanding decreases in land relative humidity with global warming: conceptual model and GCM simulations
Climate models simulate a strong land-ocean contrast in the response of
near-surface relative humidity to global warming: relative humidity tends to
increase slightly over oceans but decrease substantially over land. Surface
energy balance arguments have been used to understand the response over ocean
but are difficult to apply over more complex land surfaces. Here, a conceptual
box model is introduced, involving moisture transport between the land and
ocean boundary layers and evapotranspiration, to investigate the decreases in
land relative humidity as the climate warms. The box model is applied to
idealized and full-complexity (CMIP5) general circulation model simulations,
and it is found to capture many of the features of the simulated changes in
land relative humidity. The box model suggests there is a strong link between
fractional changes in specific humidity over land and ocean, and the greater
warming over land than ocean then implies a decrease in land relative humidity.
Evapotranspiration is of secondary importance for the increase in specific
humidity over land, but it matters more for the decrease in relative humidity.
Further analysis shows there is a strong feedback between changes in
surface-air temperature and relative humidity, and this can amplify the
influence on relative humidity of factors such as stomatal conductance and soil
moisture.Comment: Submitted to Journal of Climate on May 1st, 201
A signature of anisotropic bubble collisions
Our universe may have formed via bubble nucleation in an eternally-inflating
background. Furthermore, the background may have a compact dimension---the
modulus of which tunnels out of a metastable minimum during bubble
nucleation---which subsequently grows to become one of our three large spatial
dimensions. When in this scenario our bubble universe collides with other ones
like it, the collision geometry is constrained by the reduced symmetry of the
tunneling instanton. While the regions affected by such bubble collisions still
appear (to leading order) as disks in an observer's sky, the centers of these
disks all lie on a single great circle, providing a distinct signature of
anisotropic bubble nucleation.Comment: 10 pages, 5 figures; v2: crucial error corrected, conclusions revise
- …