925 research outputs found
Toward a description of foreigner register : an analysis of variation in the speech of native teachers of English as a foreign language
SIGLEAvailable from British Library Document Supply Centre- DSC:D41736/82 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Counting Supertubes
The quantum states of the supertube are counted by directly quantizing the
linearized Born-Infeld action near the round tube. The result is an entropy , in accord with conjectures in the
literature. As a result, supertubes may be the generic D0-F1 bound state. Our
approach also shows directly that supertubes are marginal bound states with a
discrete spectrum. We also discuss the relation to recent suggestions of Mathur
et al involving three-charge black holes.Comment: 15 pages, v2: reference corrected; v3: few corrections and explicit
derivation of a relation are added to appendix
Dwarf galaxies beyond our doorstep: the Centaurus A group
The study of dwarf galaxies in groups is a powerful tool for investigating
galaxy evolution, chemical enrichment and environmental effects on these
objects. Here we present results obtained for dwarf galaxies in the Centaurus A
complex, a dense nearby (~4 Mpc) group that contains two giant galaxies and
about 30 dwarf companions of different morphologies and stellar contents. We
use archival optical (HST/ACS) and near-infrared (VLT/ISAAC) data to derive
physical properties and evolutionary histories from the resolved stellar
populations of these dwarf galaxies. In particular, for early-type dwarfs we
are able to construct metallicity distribution functions, find population
gradients and quantify the intermediate-age star formation episodes. For
late-type dwarfs, we compute recent (~1 Gyr) star formation histories and study
their stellar distribution. We then compare these results with properties of
the dwarfs in our Milky Way and in other groups. Our work will ultimately lead
to a better understanding of the evolution of dwarf galaxies.Comment: 6 pages, 5 figures; to appear in the proceedings of the conference "A
Universe of dwarf galaxies" (Lyon, June 14-18, 2010
Cooling and the SU(2) Instanton Vaccuum
We present results of an investigation into the nature of instantons in
4-dimensional pure gauge lattice \ obtained from configurations which
have been cooled using an under-relaxed cooling algorithm. We discuss ways of
calibrating the cooling and the effects of different degrees of cooling, and
compare our data for the shapes, sizes and locations of instantons with
continuum results. In this paper we extend the ideas and techniques developed
by us for use in , and compare the results with those obtained by other
groups.Comment: 22 pages, LaTeX, uuencoded compressed tarfile of figures sent
separately. Full (compressed) postscript version (118k)available from
ftp://rock.helsinki.fi/pub/preprints/tft/Year1995/HU-TFT-95-21/paper.ps.
SU(N) Evolution of a Frustrated Spin Ladder
Recent studies indicate that the weakly coupled spin-1/2 Heisenberg
antiferromagnet with next nearest neighbor frustration supports massive spinons
when suitably tuned. The straightforward SU(N) generalization of the low energy
ladder Hamiltonian yields two independent SU(N) Thirring models with N-1
multiplets of massive ``spinon'' excitations. We study the evolution of the
complete set of low-energy dynamical structure factors using form factors.
Those corresponding to the smooth (staggered) magnetizations are qualitatively
different (the same) in the N=2 and N>2 cases. The absence of single-particle
peaks preserves the notion of spinons stabilized by frustration. In contrast to
the ladder, we note that the N=infinity limit of the four chain magnet is not a
trivial free theory.Comment: 10 pages, RevTex, 5 figures; SU(N) approach clarifie
Banning the bulb: institutional evolution and the phased ban of incandescent lighting in Germany
Much academic attention has been directed at analysing energy efficiency investments through the lens of âbehavioural failureâ. These studies have challenged the neoclassical framing of regulation which emphasises the efficiency benefits of price based policy, underpinned by the notion of rational individual self-mastery. The increasing use of a regulatory ban on electric lamps in many countries is one of the most recent and high profile flash points in this dialectic of âfreedom-versus-the-stateâ in the public policy discourse. This paper interrogates this debate through a study of electric lamp diffusion in Germany. It is argued that neoclassical theory and equilibrium analysis is inadequate as a tool for policy analysis as it takes the formation of market institutions, such as existing regulations, for granted. Further still, it may be prone to encourage idealistic debates around such grand narratives which may in practice simply serve those who benefit most from the status quo. Instead we argue for an evolutionary approach which we suggest offers a more pragmatic framing tool which focuses on the formation of market institutions in light of shifting social norms and political goalsâin our case, progress towards energy efficiency and environmental goals
Charged Higgs Observability Through Associated Production With W at a Muon Collider
The observability of a charged Higgs boson produced in association with a W
boson at future muon colliders is studied. The analysis is performed within the
MSSM framework. The charged Higgs is assumed to decay to tb and a fully
hadronic final state is analyzed, i.e., mu+mu- \rightarrow H\pmW\mp \rightarrow
tbW \rightarrow WbbW \rightarrow jjjjbb. The main background is tt production
in fully hadronic final state which is an irreducible background with very
similar kinematic features. It is shown that although the discovery potential
is almost the same for a charged Higgs mass in the range 200 GeV < mH\pm < 400
GeV, the signal significance is about 1sigma for tanbeta = 50 at integrated
luminosity of 50 fb-1. The signal rate is well above that at e+e- linear
colliders with the same center of mass energy and enough data (O(1 ab-1)) will
provide the same discovery potential for all heavy charged Higgs masses up to
mH\pm \sim 400 GeV, however, the muon collider cannot add anything to the LHC
findings.Comment: 18 pages, 11 figure
Fermions from Half-BPS Supergravity
We discuss collective coordinate quantization of the half-BPS geometries of
Lin, Lunin and Maldacena (hep-th/0409174). The LLM geometries are parameterized
by a single function on a plane. We treat this function as a collective
coordinate. We arrive at the collective coordinate action as well as path
integral measure by considering D3 branes in an arbitrary LLM geometry. The
resulting functional integral is shown, using known methods (hep-th/9309028),
to be the classical limit of a functional integral for free fermions in a
harmonic oscillator. The function gets identified with the classical limit
of the Wigner phase space distribution of the fermion theory which satisfies u
* u = u. The calculation shows how configuration space of supergravity becomes
a phase space (hence noncommutative) in the half-BPS sector. Our method sheds
new light on counting supersymmetric configurations in supergravity.Comment: 28 pages, 2 figures, epsf;(v3) eq. (3.3) clarified and notationally
simplified; version to appear in JHE
Generating droplets in two-dimensional Ising spin glasses by using matching algorithms
We study the behavior of droplets for two dimensional Ising spin glasses with
Gaussian interactions. We use an exact matching algorithm which enables study
of systems with linear dimension L up to 240, which is larger than is possible
with other approaches. But the method only allows certain classes of droplets
to be generated. We study single-bond, cross and a category of fixed volume
droplets as well as first excitations. By comparison with similar or equivalent
droplets generated in previous works, the advantages but also the limitations
of this approach are revealed. In particular we have studied the scaling
behavior of the droplet energies and droplet sizes. In most cases, a crossover
of the data can be observed such that for large sizes the behavior is
compatible with the one-exponent scenario of the droplet theory. Only for the
case of first excitations, no clear conclusion can be reached, probably because
even with the matching approach the accessible system sizes are still too
small.Comment: 11 pages, 16 figures, revte
Relativistic nuclear recoil corrections to the energy levels of hydrogen-like and high lithium like atoms in all orders in
The relativistic nuclear recoil corrections to the energy levels of
low-laying states of hydrogen-like and high lithium-like atoms in all
orders in are calculated. The calculations are carried out using the
B-spline method for the Dirac equation.
For low the results of the calculation are in good agreement with the
-expansion results. It is found that the nuclear recoil
contribution, additional to the Salpeter's one, to the Lamb shift () of
hydrogen is . The total nuclear recoil correction to the energy
of the transition in lithium-like uranium
constitutes and is largely made up of QED contributions.Comment: 19 pages, latex, accepted for publication in Phys. Rev.
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