4,611 research outputs found
Quasiparticle Description of Hot QCD at Finite Quark Chemical Potential
We study the extension of a phenomenologically successful quasiparticle model
that describes lattice results of the equation of state of the deconfined phase
of QCD for Tc <= T < 4 Tc, to finite quark chemical potential mu. The phase
boundary line Tc(mu), the pressure difference (p(T,mu)-p(T,mu=0))/T^4 and the
quark number density nq(T,mu)/T^3 are calculated and compared to recent lattice
results. Good agreement is found up to quark chemical potentials of order mu =
Tc.Comment: 12 pages, 7 figures; added reference
Why do people opt-out or not opt-out of automatic enrolment? A focus group study of automatic enrolment into a workplace pension in the United Kingdom
Automatic enrolment (AE) into a workplace pension is an important recent development in pension policy. An important question for this policy is why do people opt-out or not opt-out of AE? This question is important for understanding the power of suggestion associated with AE as well as responding to concerns that women might face undue pressure to opt-out. This article addresses this question through a focus group study into the United Kingdom’s new AE policy. Women were more likely than men to cite lack of affordability as a reason for opting out. Lack of information also seemed important for the power of suggestion associated with AE. Further research should explore how to make AE less gender blind as well as the types of information or advice that should be provided alongside AE
Gauge theory of Faddeev-Skyrme functionals
We study geometric variational problems for a class of nonlinear sigma-models
in quantum field theory. Mathematically, one needs to minimize an energy
functional on homotopy classes of maps from closed 3-manifolds into compact
homogeneous spaces G/H. The minimizers are known as Hopfions and exhibit
localized knot-like structure. Our main results include proving existence of
Hopfions as finite energy Sobolev maps in each (generalized) homotopy class
when the target space is a symmetric space. For more general spaces we obtain a
weaker result on existence of minimizers in each 2-homotopy class.
Our approach is based on representing maps into G/H by equivalence classes of
flat connections. The equivalence is given by gauge symmetry on pullbacks of
G-->G/H bundles. We work out a gauge calculus for connections under this
symmetry, and use it to eliminate non-compactness from the minimization problem
by fixing the gauge.Comment: 34 pages, no figure
The Littlest Higgs in Anti-de Sitter Space
We implement the SU(5)/SO(5) littlest Higgs theory in a slice of 5D Anti-de
Sitter space bounded by a UV brane and an IR brane. In this model, there is a
bulk SU(5) gauge symmetry that is broken to SO(5) on the IR brane, and the
Higgs boson is contained in the Goldstones from this breaking. All of the
interactions on the IR brane preserve the global symmetries that protect the
Higgs mass, but a radiative potential is generated through loops that stretch
to the UV brane where there are explicit SU(5) violating boundary conditions.
Like the original littlest Higgs, this model exhibits collective breaking in
that two interactions must be turned on in order to generate a Higgs potential.
In AdS space, however, collective breaking does not appear in coupling
constants directly but rather in the choice of UV brane boundary conditions. We
match this AdS construction to the known low energy structure of the littlest
Higgs and comment on some of the tensions inherent in the AdS construction. We
calculate the 5D Coleman-Weinberg effective potential for the Higgs and find
that collective breaking is manifest. In a simplified model with only the SU(2)
gauge structure and the top quark, the physical Higgs mass can be of order 200
GeV with no considerable fine tuning (25%). We sketch a more realistic model
involving the entire gauge and fermion structure that also implements T-parity,
and we comment on the tension between T-parity and flavor structure.Comment: 42 pages, 7 figures, 3 tables; v2: minor rewording, JHEP format; v3:
to match JHEP versio
Operator renewal theory and mixing rates for dynamical systems with infinite measure
We develop a theory of operator renewal sequences in the context of infinite
ergodic theory. For large classes of dynamical systems preserving an infinite
measure, we determine the asymptotic behaviour of iterates of the
transfer operator. This was previously an intractable problem.
Examples of systems covered by our results include (i) parabolic rational
maps of the complex plane and (ii) (not necessarily Markovian) nonuniformly
expanding interval maps with indifferent fixed points.
In addition, we give a particularly simple proof of pointwise dual ergodicity
(asymptotic behaviour of ) for the class of systems under
consideration.
In certain situations, including Pomeau-Manneville intermittency maps, we
obtain higher order expansions for and rates of mixing. Also, we obtain
error estimates in the associated Dynkin-Lamperti arcsine laws.Comment: Preprint, August 2010. Revised August 2011. After publication, a
minor error was pointed out by Kautzsch et al, arXiv:1404.5857. The updated
version includes minor corrections in Sections 10 and 11, and corresponding
modifications of certain statements in Section 1. All main results are
unaffected. In particular, Sections 2-9 are unchanged from the published
versio
Antiferromagnetic ordering in the absence of a structural distortion in Ba(Fe{1-x}Mn{x})2As2
Neutron and x-ray diffraction studies of Ba(Fe{1-x}Mn{x})2As2 for low doping
concentrations (x <= 0.176) reveal that at a critical concentration, 0.102 < x
< 0.118, the tetragonal-to-orthorhombic transition abruptly disappears whereas
magnetic ordering with a propagation vector of (1/2 1/2 1) persists. Among all
of the iron arsenides this observation is unique to Mn-doping, and unexpected
because all models for "stripe-like" antiferromagnetic order anticipate an
attendant orthorhombic distortion due to magnetoelastic effects. We discuss
these observations and their consequences in terms of previous studies of
Ba(Fe{1-x}TM{x})2As2 compounds (TM = Transition Metal), and models for magnetic
ordering in the iron arsenide compounds.Comment: 5 pages, 4 figures; accepted for publication in Phys. Rev. B Rapid
Com
Suppression of antiferromagnetic order and orthorhombic distortion in superconducting Ba(Fe0.961Rh0.039)2As2
Neutron diffraction and high-resolution x-ray diffraction studies find that,
similar to the closely related underdoped Ba(Fe[1-x]Cox)2As2 superconducting
compounds, Ba(Fe0.961Rh0.039)2As2 shows strong evidence of competition and
coexistence between superconductivity and antiferromagnetic order below the
superconducting transition, Tc = 14 K. The transition temperatures for both the
magnetic order and orthorhombic distortion are in excellent agreement with
those inferred from resistivity measurements, and both order parameters
manifest a distinct decrease in magnitude below Tc. These data suggest that the
strong interaction between magnetism and superconductivity is a general feature
of electron-doped Ba(Fe[1-x]TMx)2As2 superconductors (TM = Transition Metal).Comment: 4 pages, 4 figure
- …