19,566 research outputs found
Splitting The Gluon?
In the strongly correlated environment of high-temperature cuprate
superconductors, the spin and charge degrees of freedom of an electron seem to
separate from each other. A similar phenomenon may be present in the strong
coupling phase of Yang-Mills theories, where a separation between the color
charge and the spin of a gluon could play a role in a mass gap formation. Here
we study the phase structure of a decomposed SU(2) Yang-Mills theory in a mean
field approximation, by inspecting quantum fluctuations in the condensate which
is formed by the color charge component of the gluon field. Our results suggest
that the decomposed theory has an involved phase structure. In particular,
there appears to be a phase which is quite reminiscent of the superconducting
phase in cuprates. We also find evidence that this phase is separated from the
asymptotically free theory by an intermediate pseudogap phase.Comment: Improved discussion of magnetic nature of phases; removed
unsubstantiated speculation about color confinemen
Bag Formation in Quantum Hall Ferromagnets
Charged skyrmions or spin-textures in the quantum Hall ferromagnet at filling
factor nu=1 are reinvestigated using the Hartree-Fock method in the lowest
Landau level approximation. It is shown that the single Slater determinant with
the minimum energy in the unit charge sector is always of the hedgehog form. It
is observed that the magnetization vector's length deviates locally from unity,
i.e. a bag is formed which accommodates the excess charge. In terms of a
gradient expansion for extended spin-textures a novel O(3) type of effective
action is presented, which takes bag formation into account.Comment: 13 pages, 3 figure
Nearest pattern interaction and global pattern formation
We studied the effect of nearest pattern interaction on a globally pattern
formation in a 2-dimensional space, where patterns are to grow initially from a
noise in the presence of periodic supply of energy. Although our approach is
general, we found that this study is relevant in particular to the pattern
formation on a periodically vibrated granular layer, as it gives a unified
perspective of the experimentally observed pattern dynamics such as oscillon
and stripe formations, skew-varicose and crossroll instabilities, and also a
kink formation and decoration
Dementia Caregiving Research: Expanding and Reframing the Lens of Diversity, Inclusivity, and Intersectionality
This forum expands and reframes the lens of dementia caregiving research among diverse racial and ethnic groups to better understand the unique needs, stressors, and strengths of multicultural and racial-ethnic family caregivers in the United States. By providing more diverse and inclusive knowledge on caregiving to older adults in the United States, we can create a new path forward with regards to caregiving research. Throughout the article, major questions and answers are supported by critiquing some of the caregiving literature. Discussions are provided to help create inclusive ways of conceptualizing caregiving research and using methodological approaches to reflect the diversity of caregivers and care recipients in the United States. Expanding and reframing the conceptual and methodological lens of diversity, inclusivity and intersectionality can provide evidence to support effective policy, practice, and care in addressing the needs of diverse groups of caregivers and older adults living with dementia
Bell's inequality with Dirac particles
We study Bell's inequality using the Bell states constructed from four
component Dirac spinors. Spin operator is related to the Pauli-Lubanski pseudo
vector which is relativistic invariant operator. By using Lorentz
transformation, in both Bell states and spin operator, we obtain an observer
independent Bell's inequality, so that it is maximally violated as long as it
is violated maximally in the rest frame.Comment: 7 pages. arXiv admin note: text overlap with arXiv:quant-ph/0308156
by other author
Comparative assessment of young learners' foreign language competence in three Eastern European countries
This paper concerns teacher practices in, and beliefs about, the assessment of young learners' progress in English in three Eastern European countries (Slovenia, Croatia, and the Czech Republic). The central part of the paper focuses on an international project involving empirical research into assessment of young learners' foreign language competence in Slovenia, Croatia and the Czech Republic. With the help of an adapted questionnaire, we collected data from a non-random sample of primary and foreign language teachers who teach foreign languages at the primary level in these countries. The research shows that English as a foreign language is taught mostly by young teachers either primary specialists or foreign language teachers. These teachers most frequently use oral assessment/interviews or self-developed tests. Other more authentic types of assessment, such as language portfolios, are rarely used. The teachers most frequently assess speaking and listening skills, and they use assessment involving vocabulary the most frequently of all. However, there are significant differences in practice among the three countries
The Radio Afterglow and Host Galaxy of the Dark GRB 020819
Of the fourteen gamma-ray bursts (GRBs) localized to better than 2' radius
with the SXC on HETE-2, only two lack optical afterglow detections, and the
high recovery rate among this sample has been used to argue that the fraction
of truly dark bursts is ~10%. While a large fraction of earlier dark bursts can
be explained by the failure of ground-based searches to reach appropriate
limiting magnitudes, suppression of the optical light of these SXC dark bursts
seems likely. Here we report the discovery and observation of the radio
afterglow of GRB 020819, an SXC dark burst, which enables us to identify the
likely host galaxy (probability of 99.2%) and hence the redshift (z=0.41) of
the GRB. The radio light curve is qualitatively similar to that of several
other radio afterglows, and may include an early-time contribution from the
emission of the reverse shock. The proposed host is a bright R = 19.5 mag
barred spiral galaxy, with a faint R ~ 24.0 mag "blob'' of emission, 3" from
the galaxy core (16 kpc in projection), that is coincident with the radio
afterglow. Optical photometry of the galaxy and blob, beginning 3 hours after
the burst and extending over more than 100 days, establishes strong upper
limits to the optical brightness of any afterglow or associated supernova.
Combining the afterglow radio fluxes and our earliest R-band limit, we find
that the most likely afterglow model invokes a spherical expansion into a
constant-density (rather than stellar wind-like) external environment; within
the context of this model, a modest local extinction of A_V ~ 1 mag is
sufficient to suppress the optical flux below our limits.Comment: 7 pages, 2 figures. ApJ, in press. For more info on dark bursts, see
http://www.astro.ku.dk/~pallja/dark.htm
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