4,408 research outputs found
Spin-Statistics Violations in Superstring Theory
I describe how superstring theory may violate spin-statistics in an
experimentally observable manner. Reviewing the basics of superstring
interactions and how to utilize these to produce a statistical phase, I then
apply these ideas to two specific examples. The first is the case of heterotic
worldsheet linkings, whereby one small closed string momentarily enlarges
sufficiently to pass over another, producing such a statistical phase. The
second is the braneworld model with noncommutative geometry, whereby matter
composed of open strings may couple to a background in which spacetime
coordinates do not commute, modifying the field (anti)commutator algebra. I
conclude with ways to sharpen and experimentally test these exciting avenues to
possibly verify superstring theory.Comment: 18 pages, 3 figures; v2: references added and typos correcte
Large Radius Hagedorn Regime in String Gas Cosmology
We calculate the equation of state of a gas of strings at high density in a
large toroidal universe, and use it to determine the cosmological evolution of
background metric and dilaton fields in the entire large radius Hagedorn
regime, (ln S)^{1/d} << R << S^{1/d} (with S the total entropy). The pressure
in this regime is not vanishing but of O(1), while the equation of state is
proportional to volume, which makes our solutions significantly different from
previously published approximate solutions. For example, we are able to
calculate the duration of the high-density "Hagedorn" phase, which increases
exponentially with increasing entropy, S. We go on to discuss the difficulties
of the scenario, quantifying the problems of establishing thermal equilibrium
and producing a large but not too weakly-coupled universe.Comment: 12 pages, 4 figures, more details presented in string thermodynamics
section, to be published in Physical Review
Mixed-method study of a conceptual model of evidence-based intervention sustainment across multiple public-sector service settings.
BackgroundThis study examines sustainment of an EBI implemented in 11 United States service systems across two states, and delivered in 87 counties. The aims are to 1) determine the impact of state and county policies and contracting on EBI provision and sustainment; 2) investigate the role of public, private, and academic relationships and collaboration in long-term EBI sustainment; 3) assess organizational and provider factors that affect EBI reach/penetration, fidelity, and organizational sustainment climate; and 4) integrate findings through a collaborative process involving the investigative team, consultants, and system and community-based organization (CBO) stakeholders in order to further develop and refine a conceptual model of sustainment to guide future research and provide a resource for service systems to prepare for sustainment as the ultimate goal of the implementation process.MethodsA mixed-method prospective and retrospective design will be used. Semi-structured individual and group interviews will be used to collect information regarding influences on EBI sustainment including policies, attitudes, and practices; organizational factors and external policies affecting model implementation; involvement of or collaboration with other stakeholders; and outer- and inner-contextual supports that facilitate ongoing EBI sustainment. Document review (e.g., legislation, executive orders, regulations, monitoring data, annual reports, agendas and meeting minutes) will be used to examine the roles of state, county, and local policies in EBI sustainment. Quantitative measures will be collected via administrative data and web surveys to assess EBI reach/penetration, staff turnover, EBI model fidelity, organizational culture and climate, work attitudes, implementation leadership, sustainment climate, attitudes toward EBIs, program sustainment, and level of institutionalization. Hierarchical linear modeling will be used for quantitative analyses. Qualitative analyses will be tailored to each of the qualitative methods (e.g., document review, interviews). Qualitative and quantitative approaches will be integrated through an inclusive process that values stakeholder perspectives.DiscussionThe study of sustainment is critical to capitalizing on and benefiting from the time and fiscal investments in EBI implementation. Sustainment is also critical to realizing broad public health impact of EBI implementation. The present study takes a comprehensive mixed-method approach to understanding sustainment and refining a conceptual model of sustainment
Covariant Closed String Coherent States
We give the first construction of covariant coherent closed string states,
which may be identified with fundamental cosmic strings. We outline the
requirements for a string state to describe a cosmic string, and using DDF
operators provide an explicit and simple map that relates three different
descriptions: classical strings, lightcone gauge quantum states and covariant
vertex operators. The naive construction leads to covariant vertex operators
whose existence requires a lightlike compactification of spacetime. When the
lightlike compactified states in the underlying Hilbert space are projected out
the resulting coherent states have a classical interpretation and are in
one-to-one correspondence with arbitrary classical closed string loops.Comment: 4 page
EVALUATING BIOLOGICAL AND PHYSICAL DRIVERS OF EVAPOTRANSPIRATION TRENDS AT NORTHEASTERN US WATERSHEDS
Electronic properties of disclinated flexible membrane beyond the inextensional limit: Application to graphene
Gauge-theory approach to describe Dirac fermions on a disclinated flexible
membrane beyond the inextensional limit is formulated. The elastic membrane is
considered as an embedding of 2D surface into R^3. The disclination is
incorporated through an SO(2) gauge vortex located at the origin, which results
in a metric with a conical singularity. A smoothing of the conical singularity
is accounted for by replacing a disclinated rigid plane membrane with a
hyperboloid of near-zero curvature pierced at the tip by the SO(2) vortex. The
embedding parameters are chosen to match the solution to the von Karman
equations. A homogeneous part of that solution is shown to stabilize the
theory. The modification of the Landau states and density of electronic states
of the graphene membrane due to elasticity is discussed.Comment: 15 pages, Journal of Physics:Condensed Matter in pres
Absolute diffuse calibration of IRAC through mid-infrared and radio study of HII regions
We investigate the diffuse absolute calibration of the InfraRed Array Camera
on the Spitzer Space Telescope at 8.0microns using a sample of 43 HII regions
with a wide range of morphologies near GLON=312deg. For each region we
carefully measure sky-subtracted,point-source- subtracted, areally-integrated
IRAC 8.0-micron fluxes and compare these with Midcourse Space eXperiment (MSX)
8.3-micron images at two different spatial resolutions, and with radio
continuum maps. We determine an accurate median ratio of IRAC
8.0-micron/MSX\8.3-micron fluxes, of 1.55+/-0.15. From robust spectral energy
distributions of these regions we conclude that the present 8.0-micron diffuse
calibration of the SST is 36% too high compared with the MSX validated
calibration, perhaps due to scattered light inside the camera. This is an
independent confirmation of the result derived for the diffuse calibration of
IRAC by the Spitzer Science Center (SSC).
From regression analyses we find that 843-MHz radio fluxes of HII regions and
mid-infrared (MIR) fluxes are linearly related for MSX at 8.3-microns and
Spitzer at 8.0 microns, confirming the earlier MSX result by Cohen & Green. The
median ratio of MIR/843-MHz diffuse continuum fluxes is 600 times smaller in
nonthermal than thermal regions, making it a sharp discriminant. The ratios are
largely independent of morphology up to a size of ~24 arcsec. We provide
homogeneous radio and MIR morphologies for all sources. MIR morphology is not
uniquely related to radio structure. Compact regions may have MIR filaments
and/or diffuse haloes, perhaps infrared counter- parts to weakly ionized radio
haloes found around compact HII regions. We offer two IRAC colour-colour plots
as quantitative diagnostics of diffuse HII regions.Comment: 29 pages, LaTeX (aastex), incl. 31 PostScript (ps,eps) figures and 5
tables. Accepted by MNRAS (main journal). Replaced an unused file and added
this URL for people wishing to download a version with high-resolution
images: http://www.astro.wisc.edu/sirtf/martin.hii.accepted.pd
Tapping Environmental History to Recreate America’s Colonial Hydrology
To properly remediate, improve, or predict how hydrological systems behave, it is vital to establish their histories. However, modern-style records, assembled from instrumental data and remote sensing platforms, hardly exist back more than a few decades. As centuries of data is preferable given multidecadal fluxes of both meteorology/climatology and demographics, building such a history requires resources traditionally considered only useful in the social sciences and humanities. In this Feature, Pastore et al. discuss how they have undertaken the synthesis of historical records and modern techniques to understand the hydrology of the Northeastern U.S. from Colonial times to modern day. Such approaches could aid studies in other regions that may require heavier reliance on qualitative narratives. Further, a better insight as to how historical changes unfolded could provide a “past is prologue” methodology to increase the accuracy of predictive environmental models
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