2,096 research outputs found
Non-Higgsable QCD and the Standard Model Spectrum in F-theory
Many four-dimensional supersymmetric compactifications of F-theory contain
gauge groups that cannot be spontaneously broken through geometric
deformations. These "non-Higgsable clusters" include realizations of ,
, and , but no gauge groups or factors with
. We study possible realizations of the standard model in F-theory that
utilize non-Higgsable clusters containing factors and show that there
are three distinct possibilities. In one, fields with the non-abelian gauge
charges of the standard model matter fields are localized at a single locus
where non-perturbative and seven-branes intersect; cancellation
of gauge anomalies implies that the simplest four-dimensional chiral
model that may arise in this context exhibits
standard model families. We identify specific geometries that realize
non-Higgsable and sectors. This kind of scenario
provides a natural mechanism that could explain the existence of an unbroken
QCD sector, or more generally the appearance of light particles and symmetries
at low energy scales.Comment: v1: 29 pages + reference
Matter in transition
We explore a novel type of transition in certain 6D and 4D quantum field
theories, in which the matter content of the theory changes while the gauge
group and other parts of the spectrum remain invariant. Such transitions can
occur, for example, for SU(6) and SU(7) gauge groups, where matter fields in a
three-index antisymmetric representation and the fundamental representation are
exchanged in the transition for matter in the two-index antisymmetric
representation. These matter transitions are realized by passing through
superconformal theories at the transition point. We explore these transitions
in dual F-theory and heterotic descriptions, where a number of novel features
arise. For example, in the heterotic description the relevant 6D SU(7) theories
are described by bundles on K3 surfaces where the geometry of the K3 is
constrained in addition to the bundle structure. On the F-theory side,
non-standard representations such as the three-index antisymmetric
representation of SU(N) require Weierstrass models that cannot be realized from
the standard SU(N) Tate form. We also briefly describe some other situations,
with groups such as Sp(3), SO(12), and SU(3), where analogous matter
transitions can occur between different representations. For SU(3), in
particular, we find a matter transition between adjoint matter and matter in
the symmetric representation, giving an explicit Weierstrass model for the
F-theory description of the symmetric representation that complements another
recent analogous construction.Comment: 107 pages, 3 figures, 32 tables. In version 2, one figure and
comments added on the geometry of matter transition
Letter from James Washington to James B. Finley
Washington encloses a Memorial from the Council of the Wyandot Nation. He asks Finley to present it on their behalf at the General Conference of 1848. Abstract Number - 780https://digitalcommons.owu.edu/finley-letters/2286/thumbnail.jp
Connectivity differences between Gulf War Illness (GWI) phenotypes during a test of attention
One quarter of veterans returning from the 1990–1991 Persian Gulf War have developed Gulf War Illness (GWI) with chronic pain, fatigue, cognitive and gastrointestinal dysfunction. Exertion leads to characteristic, delayed onset exacerbations that are not relieved by sleep. We have modeled exertional exhaustion by comparing magnetic resonance images from before and after submaximal exercise. One third of the 27 GWI participants had brain stem atrophy and developed postural tachycardia after exercise (START: Stress Test Activated Reversible Tachycardia). The remainder activated basal ganglia and anterior insulae during a cognitive task (STOPP: Stress Test Originated Phantom Perception). Here, the role of attention in cognitive dysfunction was assessed by seed region correlations during a simple 0-back stimulus matching task (“see a letter, push a button”) performed before exercise. Analysis was analogous to resting state, but different from psychophysiological interactions (PPI). The patterns of correlations between nodes in task and default networks were significantly different for START (n = 9), STOPP (n = 18) and control (n = 8) subjects. Edges shared by the 3 groups may represent co-activation caused by the 0-back task. Controls had a task network of right dorsolateral and left ventrolateral prefrontal cortex, dorsal anterior cingulate cortex, posterior insulae and frontal eye fields (dorsal attention network). START had a large task module centered on the dorsal anterior cingulate cortex with direct links to basal ganglia, anterior insulae, and right dorsolateral prefrontal cortex nodes, and through dorsal attention network (intraparietal sulci and frontal eye fields) nodes to a default module. STOPP had 2 task submodules of basal ganglia–anterior insulae, and dorsolateral prefrontal executive control regions. Dorsal attention and posterior insulae nodes were embedded in the default module and were distant from the task networks. These three unique connectivity patterns during an attention task support the concept of Gulf War Disease with recognizable, objective patterns of cognitive dysfunction
The Effect of Business Development Services on Performance of Small and Medium Manufacturing Enterprises in Kenya
Small and Medium Enterprises have been regarded to play significant roles of job creation, poverty alleviation and economic development of many countries worldwide. These enterprises are however affected by many
different factors. How these factors manifest singly or jointly is therefore a key concern for these organizations. Vital among these factors are business
development services that affect how organizations produce and sell their goods and services. There is however a dearth of studies focusing on effects
of aspects of business development services on organizational performance in Kenya. This study aimed at establishing how market access, procurement
services and infrastructure facilities affect performance of small and medium manufacturing enterprises in Kenya. The study adopted a cross sectional survey design and examined primary data collected from 150 enterprises in Nairobi. Inferential statistics were used to interrogate
relationships between independent variables and performance while descriptive statistics were used to determine distribution, central tendency
and dispersion and hence establish conformity to linear regression requirements. Contrary to expectation, the results for market access did not show any relationship but procurement services and infrastructure
facilities each had a positive and significant influence on performance of the enterprises. Furthermore, it was established that the joint effect of the
three variables on performance of studied firms is greater than their individual effect. This study therefore concludes that, since procurement
services and infrastructure facilities showed a positive influence on performance of small and medium manufacturing enterprises in Kenya,
these enterprises should adopt strategies that enhance procurement and improve infrastructure facilities to experience better performance
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