544 research outputs found
The Photometric Period of the Cataclysmic Variable HV Andromedae
We present four nights of time-resolved photometry of the cataclysmic
variable star HV And. Our time series analysis has revealed a prominent period
at 3.368 +/- 0.060 hours, as well as some low frequency power. We interpret
this signal, from saw-tooth waves in the light curve, as evidence of superhumps
in HV And.Comment: 7 pages, 3 figures; accepted for publication in New Astronom
The Photometric Period and Variability of the Cataclysmic Variable V849 Herculis (PG 1633+115)
We report time-resolved photometry of the cataclysmic variable V849 Her, and
measure a period of 0.1414 \pm 0.0030 days (3.394 \pm 0.072 hours). We also
present photometry taken over several weeks in 2010 and 2011, as well as light
curves from 1995 to 2011 by the American Association of Variable Star
Observers. The spectra, absolute magnitude derived from infrared magnitudes,
and variability all suggest that V849 Her is a nova-like variable. The shallow
(0.5-magnitude) low states we observe resemble the erratic low states of the VY
Sculptoris stars, although they may recur quasi-periodically over an average
cycle of 12.462 \pm 0.074 days.Comment: 18 pages, 9 figures, accepted for publication in New Astronom
The Orbital Period and Negative Superhumps of the Nova-Like Cataclysmic Variable V378 Pegasi
A radial velocity study is presented of the cataclysmic variable V378 Pegasi
(PG 2337+300). It is found to have an orbital period of 0.13858 +/- 0.00004 d
(3.32592 +/- 0.00096 hours). Its spectrum and long-term light curve suggest
that V378 Peg is a nova-like variable, with no outbursts. We use the
approximate distance and position in the Galaxy of V378 Peg to estimate E(B-V)
= 0.095, and use near-infrared magnitudes to calculate a distance of 680 +/- 90
pc and M_V = 4.68 +/- 0.70, consistent with V378 Peg being a nova-like.
Time-resolved photometry taken between 2001 and 2009 reveals a period of 0.1346
+/- 0.0004 d (3.23 +/- 0.01 hours). We identify this photometric variability to
be negative superhumps, from a precessing, tilted accretion disk. Our repeated
measurements of the photometric period of V378 Peg are consistent with this
period having been stable between 2001 and 2009, with its negative superhumps
showing coherence over as many as hundreds or even thousands of cycles.Comment: 24 pages, 19 figures, accepted for publication in New Astronom
Abelian Magnetic Monopole Dominance in Quark Confinement
We prove Abelian magnetic monopole dominance in the string tension of QCD.
Abelian and monopole dominance in low energy physics of QCD has been confirmed
for various quantities by recent Monte Carlo simulations of lattice gauge
theory. In order to prove this dominance, we use the reformulation of continuum
Yang-Mills theory in the maximal Abelian gauge as a deformation of a
topological field theory of magnetic monopoles, which was proposed in the
previous article by the author. This reformulation provides an efficient way
for incorporating the magnetic monopole configuration as a topological
non-trivial configuration in the functional integral. We derive a version of
the non-Abelian Stokes theorem and use it to estimate the expectation value of
the Wilson loop. This clearly exhibits the role played by the magnetic monopole
as an origin of the Berry phase in the calculation of the Wilson loop in the
manifestly gauge invariant manner. We show that the string tension derived from
the diagonal (abelian) Wilson loop in the topological field theory (studied in
the previous article) converges to that of the full non-Abelian Wilson loop in
the limit of large Wilson loop. Therefore, within the above reformulation of
QCD, this result (together with the previous result) completes the proof of
quark confinement in QCD based on the criterion of the area law of the full
non-Abelian Wilson loop.Comment: 33 pages, Latex, no figures, version accepted for publication in
Phys. Rev. D (additions of sec. 4.5 and references, and minor changes
Teacher Ratings of Children's Behavior Problems and Functional Impairment Across Gender and Ethnicity:Construct Equivalence of the Strengths and Difficulties Questionnaire
The present study examined construct equivalence of the teacher Strengths and Difficulties Questionnaire and compared mean scores in an ethnically diverse sample of children living in the Netherlands. Elementary schoolteachers completed the Strengths and Difficulties Questionnaire for 2,185 children aged 6 to 10 years of the four largest ethnic groups in the Netherlands, namely native Dutch (n = 684) and Moroccan (n = 702), Turkish (n = 434), and Surinamese (n = 365) immigrant children. Multigroup confirmatory factor analysis suggested the factor structure of the Strengths and Difficulties Questionnaire to be invariant across children's ethnicity and gender. Additionally, the factor structure appeared to be similar for Dutch and Surinamese teachers. However, mean scores on emotional problems, hyperactivity, conduct problems, prosocial behavior, and impairment varied significantly according to ethnicity and gender. Mean scores on peer problems differed significantly for boys and girls, but not across ethnicity. Whether mean differences reflect a method bias or actual differences in classroom behaviors is discussed and needs further research
Electromagnetic characteristics of bilayer quantum Hall systems in the presence of interlayer coherence and tunneling
The electromagnetic characteristics of bilayer quantum Hall systems in the
presence of interlayer coherence and tunneling are studied by means of a
pseudospin-texture effective theory and an algebraic framework of the
single-mode approximation, with emphasis on clarifying the nature of the
low-lying neutral collective mode responsible for interlayer tunneling
phenomena. A long-wavelength effective theory, consisting of the collective
mode as well as the cyclotron modes, is constructed. It is seen explicitly from
the electromagnetic response that gauge invariance is kept exact, this
implying, in particular, the absence of the Meissner effect in bilayer systems.
Special emphasis is placed on exploring the advantage of looking into quantum
Hall systems through their response; in particular, subtleties inherent to the
standard Chern-Simons theories are critically examined.Comment: 9 pages, Revtex, to appear in Phys. Rev.
In search of green political economy: steering markets, innovation and the case of the zero carbon homes agenda in England
Advocates of a democratic ‘Green state’ challenge Hayekian free-market environmentalist proposals for a minimal state and the emphasis of ecological modernisation discourses on technological innovation as the primary route towards ecological sustainability. However, these more strongly pro-market traditions raise important questions and provide useful insights concerning the challenges of translating the political ideology of ‘ecologism’ into practical proposals for democratic governance. Hayekian thought raises vital questions concerning the capacity of political processes to address complex challenges of coordinating the formulation and delivery of the sustainability objectives of ecologism. Scholarship on ecological modernisation and the ‘new regulation’ offer important insights into how shifting interrelationships between the state and private sector in the policy process might enable this challenge to be more effectively addressed. These areas for further developing proposals for a Green state are illustrated here through a case study of the zero carbon homes policy agenda in England
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
- …