164 research outputs found
Neutrino oscillations: Entanglement, energy-momentum conservation and QFT
We consider several subtle aspects of the theory of neutrino oscillations
which have been under discussion recently. We show that the -matrix
formalism of quantum field theory can adequately describe neutrino oscillations
if correct physics conditions are imposed. This includes space-time
localization of the neutrino production and detection processes. Space-time
diagrams are introduced, which characterize this localization and illustrate
the coherence issues of neutrino oscillations. We discuss two approaches to
calculations of the transition amplitudes, which allow different physics
interpretations: (i) using configuration-space wave packets for the involved
particles, which leads to approximate conservation laws for their mean energies
and momenta; (ii) calculating first a plane-wave amplitude of the process,
which exhibits exact energy-momentum conservation, and then convoluting it with
the momentum-space wave packets of the involved particles. We show that these
two approaches are equivalent. Kinematic entanglement (which is invoked to
ensure exact energy-momentum conservation in neutrino oscillations) and
subsequent disentanglement of the neutrinos and recoiling states are in fact
irrelevant when the wave packets are considered. We demonstrate that the
contribution of the recoil particle to the oscillation phase is negligible
provided that the coherence conditions for neutrino production and detection
are satisfied. Unlike in the previous situation, the phases of both neutrinos
from decay are important, leading to a realization of the
Einstein-Podolsky-Rosen paradox.Comment: 30 pages, 3 eps figures; presentation improved, clarifications added.
To the memory of G.T. Zatsepi
Walking Behavior in Technicolored GUTs
There exist two ways to obtain walk behavior: assuming a large number of
technifermions in the fundamental representation of the technicolor (TC) gauge
group, or a small number of technifermions, assuming that these fermions are in
higher-dimensional representations of the TC group. We propose a scheme to
obtain the walking behavior based on technicolored GUTs (TGUTs), where
elementary scalars with the TC degree of freedom may remain in the theory after
the GUT symmetry breaking.Comment: 11 pages, 1 figur
The structure of the Yang-Mills spectrum for arbitrary simple gauge algebras
The mass spectrum of pure Yang-Mills theory in 3+1 dimensions is discussed
for an arbitrary simple gauge algebra within a quasigluon picture. The general
structure of the low-lying gluelump and two-quasigluon glueball spectrum is
shown to be common to all algebras, while the lightest three-quasigluon
glueballs only exist when the gauge algebra is A, that is in
particular . Higher-lying glueballs are shown to
exist only for the A, D and E gauge
algebras. The shape of the static energy between adjoint sources is also
discussed assuming the Casimir scaling hypothesis and a funnel form; it appears
to be gauge-algebra dependent when at least three sources are considered. As a
main result, the present framework's predictions are shown to be consistent
with available lattice data in the particular case of an
gauge algebra within 't Hooft's large- limit.Comment: 21 pages, 4 figures; remarks added, typos corrected in v2. v3 to
appear in EPJ
Is American Public Administration Detached From Historical Context?: On the Nature of Time and the Need to Understand It in Government and Its Study
The study of public administration pays little attention to history. Most publications are focused on current problems (the present) and desired solutions (the future) and are concerned mainly with organizational structure (a substantive issue) and output targets (an aggregative issue that involves measures of both individual performance and organizational productivity/services). There is much less consideration of how public administration (i.e., organization, policy, the study, etc.) unfolds over time. History, and so administrative history, is regarded as a âpastâ that can be recorded for its own sake but has little relevance to contemporary challenges. This view of history is the product of a diminished and anemic sense of time, resulting from organizing the past as a series of events that inexorably lead up to the present in a linear fashion. To improve the understanding of governmentâs role and position in society, public administration scholarship needs to reacquaint itself with the nature of time.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Toward a Multifaceted Heuristic of Digital Reading to Inform Assessment, Research, Practice, and Policy
In this commentary, the author explores the tension between almost 30 years of work that has embraced increasingly complex conceptions of digital reading and recent studies that risk oversimplifying digital reading as a singular entity analogous with reading text on a screen. The author begins by tracing a line of theoretical and empirical work that both informs and complicates our understanding of digital literacy and, more specifically, digital reading. Then, a heuristic is proposed to systematically organize, label, and define a multifaceted set of increasingly complex terms, concepts, and practices that characterize the spectrum of digital reading experiences. Research that informs this heuristic is used to illustrate how more precision in defining digital reading can promote greater clarity across research methods and advance a more systematic study of promising digital reading practices. Finally, the author discusses implications for assessment, research, practice, and policy
Novel genetic loci associated with hippocampal volume
The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness
- âŠ