807 research outputs found
Spin-String Interaction in QCD Strings
I consider the question of the interaction between a QCD string and the spin
of a quark or an antiquark on whose worldline the string terminates. The
problem is analysed from the point of view of a string representation for the
expectation value of a Wilson loop for a spin-half particle. A string
representation of the super Wilson loop is obtained starting from an effective
string representation of a Wilson Loop. The action obtained in this manner is
invariant under a worldline supersymmetry and has a boundary term which
contains the spin-string interaction. For rectangular loops the spin-string
interaction vanishes and there is no spin-spin term in the resulting heavy
quark potential. On the other hand if an allowance is made for the finite
intrinsic thickness of the flux-tube, by assuming that the spin-string
interaction takes place not just at the boundary of the string world-sheet but
extends to a distance of the order of the intrinsic thickness of the flux tube,
then we do obtain a spin-spin interaction which falls as the fifth power of the
distance. Such a term was previously suggested by Kogut and Parisi in the
context of a flux-tube model of confinement.Comment: 19 pages, 1 figure; Published version with added discussion and
references in section
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Accommodations for English Language Learners on Statewide English Language Proficiency Assessment
This exploratory research study was conducted to examine federally- mandated annual English language proficiency (ELP) assessment of English language learners (ELLs) and their use of accommodations on the assessment. The literature was examined for differences and similarities between the three types of testing scenarios as well as identifying gaps in the literature for students who are both ELLs and who also have a disability and how their ELP is assessed, taking into account their disability. The results from investigating data related to ELLs with disabilities and specific accommodations used by ELLs with disabilities contributes to the limited current research available regarding this subgroup as well as how the annual ELP assessment mandate is actuated at the state, district, and classroom levels. The researchers used one stateâs existing quantitative ELP assessment data to examine types of accommodations for ELLs with disabilities on the statewide ELP assessment and then explored potential relationships between specific disabilities and accommodations used. The researchers investigated factors that contribute to the relationships between disabilities, accommodations, and performance on the ELP assessment through qualitative data from interviews with state, district, and school level personnel to further expand on results from the quantitative ELP assessment data
Excitations of torelon
The excitations of gluonic flux tube in a periodic lattice are examined.
Monte Carlo simulations from an anisotropic lattice are presented and the
comparison with effective string models is discussed.Comment: Talk at Lattice 2003; 3 pages, 4 figure
IT background of the medium-term storage of MartonvĂĄsĂĄr Cereal Genebank resources in phytotron cold rooms
Genebanks are storage facilities designed to maintain the plant genetic resources of
crop varieties (and their wild relatives) and to ensure that they are made available and
distributed for use by plant breeders, researchers and farmers. The MartonvĂĄsĂĄr Cereal
Genebank (MV-CGB) collection evolved from the working collections of local breeders
and consists predominantly of local and regional materials. Established in 1992 by the
Agricultural Research Institute of the Hungarian Academy of Sciences (BedĆ, 2009), MVCGB
with its over 10,000 accessions of the major species (Triticum, Aegilops, Agropyron,
Elymus, Thinopyrum, Pseudoroegneria, Secale, Hordeum, Avena, Zea mays), became one
of the approx. 80 cereal germplasm collections that exist globally. In MartonvĂĄsĂĄr
breeding is underway on a number of cereal species, and large numbers of genotypes are
tested each year in the field and under laboratory conditions. The increasing size of the
research programmes assisted by a modern genebank background involve an enormous
increase in the quantity of data that must be handled during research activities such as
traditional breeding, pre-breeding and organic breeding. A computerized system is of
primary importance to synchronize breeding and genebank activities, to monitor the
quality and quantity of seed accessions in cold storage, to assist the registration of samples,
and to facilitate characterization, regeneration and germplasm distribution
String-like behaviour of 4d SU(3) Yang-Mills flux tubes
We present here results on the fine structure of the static q\bar q potential
in d=4 SU(3) Yang-Mills theory. The potential is obtained from Polyakov loop
correlators having separations between 0.3 and 1.2 fermi. Measurements were
carried out on lattices of spatial extents of about 4 and 5.4 fermi. The
temporal extent was 5.4 fermi in both cases. The results are analyzed in terms
of the force between a q\bar q pair as well as in terms of a scaled second
derivative of the potential. The data is accurate enough to distinguish between
different effective string models and it seems to favour the expression for
ground state energy of a Nambu-Goto string.Comment: 9 pages in LaTeX with 2 figures and 2 tables in JHEP style. Replaced
to match with shortened published versio
How to Put a Heavier Higgs on the Lattice
Lattice work, exploring the Higgs mass triviality bound, seems to indicate
that a strongly interacting scalar sector in the minimal standard model cannot
exist while low energy QCD phenomenology seems to indicate that it could. We
attack this puzzle using the 1/N expansion and discover a simple criterion for
selecting a lattice action that is more likely to produce a heavy Higgs
particle. Our large calculation suggests that the Higgs mass bound might be
around , which is about 30% higher than previously obtained
Quark confinement and the bosonic string
Using a new type of simulation algorithm for the standard SU(3) lattice gauge
theory that yields results with unprecedented precision, we confirm the
presence of a correction to the static quark potential at large
distances , with a coefficient as predicted by the bosonic string
theory. In both three and four dimensions, the transition from perturbative to
string behaviour is evident from the data and takes place at surprisingly small
distances.Comment: TeX source, 21 pages, figures include
New Physics and the Landau Pole
In scalar field theories the Landau pole is an ultraviolet singularity in the
running coupling constant that indicates a mass scale at which the theory
breaks down and new physics must intervene. However, new physics at the pole
will in general affect the running of the low energy coupling constant, which
will in turn affect the location of the pole and the related upper limit
(``triviality'' bound) on the low energy coupling constant. If the new physics
is strongly coupled to the scalar fields these effects can be significant even
though they are power suppressed. We explore the possible range of such effects
by deriving the one loop renormalization group equations for an effective
scalar field theory with a dimension 6 operator representing the low energy
effects of the new physics. As an independent check we also consider a
renormalizable model of the high-scale physics constructed so that its low
energy limit coincides with the effective theory.Comment: 26 pages, 5 figure
A protosolar nebula origin for the ices agglomerated by Comet 67P/Churyumov-Gerasimenko
The nature of the icy material accreted by comets during their formation in
the outer regions of the protosolar nebula is a major open question in
planetary science. Some scenarios of comet formation predict that these bodies
agglomerated from crystalline ices condensed in the protosolar nebula.
Concurrently, alternative scenarios suggest that comets accreted amorphous ice
originating from the interstellar cloud or from the very distant regions of the
protosolar nebula. On the basis of existing laboratory and modeling data, we
find that the N/CO and Ar/CO ratios measured in the coma of the Jupiter
family comet 67P/Churyumov-Gerasimenko by the ROSINA instrument aboard the
European Space Agency's Rosetta spacecraft match those predicted for gases
trapped in clathrates. If these measurements are representative of the bulk
N/CO and Ar/CO ratios in 67P/Churyumov-Gerasimenko, it implies that the
ices accreted by the comet formed in the nebula and do not originate from the
interstellar medium, supporting the idea that the building blocks of outer
solar system bodies have been formed from clathrates and possibly from pure
crystalline ices. Moreover, because 67P/Churyumov-Gerasimenko is impoverished
in Ar and N, the volatile enrichments observed in Jupiter's atmosphere
cannot be explained solely via the accretion of building blocks with similar
compositions and require an additional delivery source. A potential source may
be the accretion of gas from the nebula that has been progressively enriched in
heavy elements due to photoevaporation.Comment: The Astrophysical Journal Letters, in pres
Observation of Anomalous Internal Pair Creation in Be: A Possible Signature of a Light, Neutral Boson
Electron-positron angular correlations were measured for the isovector
magnetic dipole 17.6 MeV state (, ) ground state
(, ) and the isoscalar magnetic dipole 18.15 MeV (,
) state ground state transitions in Be. Significant
deviation from the internal pair creation was observed at large angles in the
angular correlation for the isoscalar transition with a confidence level of . This observation might indicate that, in an intermediate step, a
neutral isoscalar particle with a mass of 16.70 (stat)
(sys) MeV and was created.Comment: 5 pages, 5 figure
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