17,988 research outputs found
Self-Tuning at Large (Distances): 4D Description of Runaway Dilaton Capture
We complete here a three-part study (see also arXiv:1506.08095 and
1508.00856) of how codimension-two objects back-react gravitationally with
their environment, with particular interest in situations where the transverse
`bulk' is stabilized by the interplay between gravity and flux-quantization in
a dilaton-Maxwell-Einstein system such as commonly appears in
higher-dimensional supergravity and is used in the Supersymmetric Large Extra
Dimensions (SLED) program. Such systems enjoy a classical flat direction that
can be lifted by interactions with the branes, giving a mass to the would-be
modulus that is smaller than the KK scale. We construct the effective
low-energy 4D description appropriate below the KK scale once the transverse
extra dimensions are integrated out, and show that it reproduces the
predictions of the full UV theory for how the vacuum energy and modulus mass
depend on the properties of the branes and stabilizing fluxes. In particular we
show how this 4D theory learns the news of flux quantization through the
existence of a space-filling four-form potential that descends from the
higher-dimensional Maxwell field. We find a scalar potential consistent with
general constraints, like the runaway dictated by Weinberg's theorem. We show
how scale-breaking brane interactions can give this potential minima for which
the extra-dimensional size, , is exponentially large relative to
underlying physics scales, , with where
can be arranged with a small hierarchy between fundamental
parameters. We identify circumstances where the potential at the minimum can
(but need not) be parametrically suppressed relative to the tensions of the
branes, provide a preliminary discussion of the robustness of these results to
quantum corrections, and discuss the relation between what we find and earlier
papers in the SLED program.Comment: 37 pages + appendice
The Gravity of Dark Vortices: Effective Field Theory for Branes and Strings Carrying Localized Flux
A Nielsen-Olesen vortex usually sits in an environment that expels the flux
that is confined to the vortex, so flux is not present both inside and outside.
We construct vortices for which this is not true, where the flux carried by the
vortex also permeates the `bulk' far from the vortex. The idea is to mix the
vortex's internal gauge flux with an external flux using off-diagonal kinetic
mixing. Such `dark' vortices could play a phenomenological role in models with
both cosmic strings and a dark gauge sector. When coupled to gravity they also
provide explicit ultra-violet completions for codimension-two brane-localized
flux, which arises in extra-dimensional models when the same flux that
stabilizes extra-dimensional size is also localized on space-filling branes
situated around the extra dimensions. We derive simple formulae for observables
such as defect angle, tension, localized flux and on-vortex curvature when
coupled to gravity, and show how all of these are insensitive to much of the
microscopic details of the solutions, and are instead largely dictated by
low-energy quantities. We derive the required effective description in terms of
a world-sheet brane action, and derive the matching conditions for its
couplings. We consider the case where the dimensions transverse to the bulk
compactify, and determine how the on- and off-vortex curvatures and other bulk
features depend on the vortex properties. We find that the brane-localized flux
does not gravitate, but just renormalizes the tension in a magnetic-field
independent way. The existence of an explicit UV completion puts the effective
description of these models on a more precise footing, verifying that
brane-localized flux can be consistent with sensible UV physics and resolving
some apparent paradoxes that can arise with a naive (but commonly used)
delta-function treatment of the brane's localization within the bulk.Comment: 36 pages + appendices, 7 figure
Probing the Structure of the Pomeron
We suggest that the pseudo-rapidity cut dependence of diffractive
deep-inelastic scattering events at HERA may provide a sensitive test of models
of diffraction. A comparison with the experimental cross section shows that the
Donnachie-Landshoff model and a simple two-gluon exchange model of the pomeron
model are disfavoured. However a model with a direct coupling of the pomeron to
quarks is viable for a harder quark--pomeron form factor, as is a model based
on the leading-twist operator contribution. We also consider a direct-coupling
scalar pomeron model. We comment on the implications of these results for the
determination of the partonic structure of the pomeron.Comment: 33 pages, LaTeX2e, 14 figures, uses axodra
EFT for Vortices with Dilaton-dependent Localized Flux
We study how codimension-two objects like vortices back-react gravitationally
with their environment in theories (such as 4D or higher-dimensional
supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system.
We do so both in the full theory, for which the vortex is an explicit classical
`fat brane' solution, and in the effective theory of `point branes' appropriate
when the vortices are much smaller than the scales of interest for their
back-reaction (such as the transverse Kaluza-Klein scale). We extend the
standard Nambu-Goto description to include the physics of flux-localization
wherein the ambient flux of the external Maxwell field becomes partially
localized to the vortex, generalizing the results of a companion paper to
include dilaton-dependence for the tension and localized flux. In the effective
theory, such flux-localization is described by the next-to-leading effective
interaction, and the boundary conditions to which it gives rise are known to
play an important role in how (and whether) the vortex causes supersymmetry to
break in the bulk. We track how both tension and localized flux determine the
curvature of the space-filling dimensions. Our calculations provide the tools
required for computing how scale-breaking vortex interactions can stabilize the
extra-dimensional size by lifting the dilaton's flat direction. For small
vortices we derive a simple relation between the near-vortex boundary
conditions of bulk fields as a function of the tension and localized flux in
the vortex action that provides the most efficient means for calculating how
physical vortices mutually interact without requiring a complete construction
of their internal structure. In passing we show why a common procedure for
doing so using a -function can lead to incorrect results. Our
procedures generalize straightforwardly to general co-dimension objects.Comment: 45 pages + appendix, 6 figure
Ranking Australian universities: controlling for scope
Rankings of universities that are based on aggregate measures ignore the discipline coverage within institutions. In this paper, for each of Australia’s 37 public universities, performance in research and teaching in broad discipline groups is evaluated and then aggregated up to obtain whole-of-institution rankings. Relative staff numbers are used as weights to aggregate research performance; student numbers are used to weight teaching performance. The performance attributes chosen are those that contribute to international academic standing. The rankings of ANU and some technologically oriented universities are raised when scope is allowed for, but elsewhere the changes are minor
Safe But Not Wholesome: The Troubling State of Trans Fat Regulation
On March 7, 2007, the New York Times reported that Starbucks, the retail coffee chain which sells millions of baked goods every day from its over 8,700 U.S. stores, had asked its suppliers to eliminate all trans fats from their products by the end of the year. The big story for New York readers, though, was not that Starbucks was requiring the elimination of trans fats from its baked goods. In fact, New York City had just passed an ordinance strictly limiting the use of artificial trans fats, the type present in partially hydrogenated vegetable oil (PHVO), by virtually all of the city\u27s food service establishments. Rather, the scoop for New York readers was the source of the trans fats being eliminated by Starbucks\u27 bakeries - butter
HAL/SM system software requirements specification
For abstract, see N76-14843
HAL/SM language specification
A programming language is presented for the flight software of the NASA Space Shuttle program. It is intended to satisfy virtually all of the flight software requirements of the space shuttle. To achieve this, it incorporates a wide range of features, including applications-oriented data types and organizations, real time control mechanisms, and constructs for systems programming tasks. It is a higher order language designed to allow programmers, analysts, and engineers to communicate with the computer in a form approximating natural mathematical expression. Parts of the English language are combined with standard notation to provide a tool that readily encourages programming without demanding computer hardware expertise. Block diagrams and flow charts are included. The semantics of the language is discussed
A model not a prophet:Operationalising patient-level prediction using observational data networks
Improving prediction model developement and evaluation processes using observational health data
A model not a prophet:Operationalising patient-level prediction using observational data networks
Improving prediction model developement and evaluation processes using observational health data
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