12,047 research outputs found
A new spin-2 self-dual model in
There are three self-dual models of massive particles of helicity +2 (or -2)
in . Each model is of first, second, and third-order in derivatives.
Here we derive a new self-dual model of fourth-order, \cL {SD}^{(4)}, which
follows from the third-order model (linearized topologically massive gravity)
via Noether embedment of the linearized Weyl symmetry. In fact, each self-dual
model can be obtained from the previous one \cL {SD}^{(i)} \to \cL
{SD}^{(i+1)}, i=1,2,3 by the Noether embedment of an appropriate gauge
symmetry, culminating in \cL {SD}^{(4)}. The new model may be identified with
the linearized version of \cL {HDTMG} = \epsilon^{\mu\nu\rho}
\Gamma_{\mu\gamma}^\epsilon (\p_\nu\Gamma_{\epsilon\rho}^\gamma +
(2/3)\Gamma_{\nu\delta}^\gamma \Gamma_{\rho\epsilon}^\delta) /8 m +
\sqrt{-g}(R_{\mu\nu} R^{\nu\mu} - 3 R^2/8) /2 m^2 . We also construct a master
action relating the third-order self-dual model to \cL {SD}^{(4)} by means of
a mixing term with no particle content which assures spectrum equivalence of
\cL {SD}^{(4)} to other lower-order self-dual models despite its pure higher
derivative nature and the absence of the Einstein-Hilbert action. The relevant
degrees of freedom of \cL {SD}^{(4)} are encoded in a rank-two tensor which
is symmetric, traceless and transverse due to trivial (non-dynamic) identities,
contrary to other spin-2 self-dual models. We also show that the Noether
embedment of the Fierz-Pauli theory leads to the new massive gravity of
Bergshoeff, Hohm and Townsend.Comment: 14 pages, no figures, typos fixed, reference (19) modifie
Consequences of Leading-Logarithm Summation for the Radiative Breakdown of Standard-Model Electroweak Symmetry
In the empirically sensible limit in which QCD, t-quark Yukawa, and
scalar-field-interaction coupling constants dominate all other Standard-Model
coupling constants, we sum all leading-logarithm terms within the perturbative
expansion for the effective potential that contribute to the extraction of the
Higgs boson mass via radiative electroweak symmetry breaking. A Higgs boson
mass of 216 GeV emerges from such terms, as well as a scalar-field-interaction
coupling constant substantially larger than that anticipated from conventional
spontaneous symmetry breaking. The sum of the effective potential's leading
logarithms is shown to exhibit a local minimum in the limit if the
QCD coupling constant is sufficiently strong, suggesting (in a multiphase
scenario) that electroweak physics may provide the mechanism for choosing the
asymptotically-free phase of QCD.Comment: latex using aip proceedings class. 8 page write-out of presentation
at MRST 2003 Conference (Syracuse
The Suprafroth (Superconducting Froth)
The structure and dynamics of froths have been subjects of intense interest
due to the desire to understand the behaviour of complex systems where
topological intricacy prohibits exact evaluation of the ground state. The
dynamics of a traditional froth involves drainage and drying in the cell
boundaries, thus it is irreversible. We report a new member to the froths
family: suprafroth, in which the cell boundaries are superconducting and the
cell interior is normal phase. Despite very different microscopic origin,
topological analysis of the structure of the suprafroth shows that statistical
von Neumann and Lewis laws apply. Furthermore, for the first time in the
analysis of froths there is a global measurable property, the magnetic moment,
which can be directly related to the suprafroth structure. We propose that this
suprafroth is a new, model system for the analysis of the complex physics of
two-dimensional froths
Local status and power in area-based health improvement partnerships
This is the authors' PDF version of an article published in Health© 2014. The definitive version is available at http://hea.sagepub.comArea-based initiatives (ABIs) have formed an important part of public policy towards more socio-economically deprived areas in many countries. Co-ordinating service provision within and across sectors has been a common feature of these initiatives. Despite sustained policy interest in ABIs, little empirical work has explored relations between ABI providers and partnership development within this context remains under-theorised. This paper addresses both of these gaps by exploring partnerships as a social and developmental process, drawing on concepts from figurational sociology to explain how provider relations develop within an ABI. Qualitative methods were used to explore, prospectively, the development of an ABI targeted at a town in the north west of England. A central finding was that, although effective delivery of ABIs is premised on a high level of coordination between service providers, the pattern of interdependencies between providers limits the frequency and effectiveness of cooperation. In particular, the interdependency of ABI providers with others in their organisation (what is termed here âorganisational pullâ) constrained the ways in which they worked with providers outside of their own organisations. âLocalâ status, which could be earned over time, enabled some providers to exert greater control over the way in which provider relations developed during the course of the initiative. These findings demonstrate how historically constituted social networks, within which all providers are embedded, shape partnership development. The theoretical insight developed here suggests a need for more realistic expectations among policy makers about how and to what extent provider partnerships can be managed. Keywords: partnership, collaboration, community services, area-based initiatives, organisational pull, figurational sociologyNational Health Service (NHS
Higher Order Stability of a Radiatively Induced 220 GeV Higgs Mass
The effective potential for radiatively broken electroweak symmetry in the
single Higgs doublet Standard Model is explored to four sequentially subleading
logarithm-summation levels (5-loops) in the dominant Higgs self-interaction
couplant . We augment these results with all contributing leading
logarithms in the remaining large but sub-dominant Standard Model couplants
(t-quark, QCD and gauge couplants) as well as next to
leading logarithm contributions from the largest of these, the t-quark and QCD
couplants. Order-by-order stability is demonstrated for earlier leading
logarithm predictions of an order 220 GeV Higgs boson mass in conjunction with
fivefold enhancement of the value for over that anticipated from
conventional spontaneous symmetry breaking.Comment: revtex, 6 pages. Analysis and text is expanded in revised versio
Transverse Coherent Instabilities in the Presence of Linear Coupling
Strong coupling between the transverse planes of a particle beam leads to an "equipartition" of the oscillation energy, including the growth rates in the case of coherent instability. The aim of this paper is to give a general formula, which includes linear coupling and which extends to two dimensions the one-dimensional results of transverse coherent instabilities. From this equation, previous results are recovered as expected: (i) Sacherer's formula for the coherent modes of oscillation, (ii) Kohaupt's formula for the mode coupling instability, and (iii) the coupled Landau damping mechanism (transfer of frequency spread), which includes the sharing of the instability growth rates. Measurements have been performed in the CERN PS, which confirm the predicted beneficial effect of coupling by both frequency spread and chromaticity sharing
Control of Coherent Instabilities by Linear Coupling
One of the main challenges in the design of high-energy colliders is the very high luminosity necessary to provide significant event rates. This imposes strong constraints to achieve and preserve beams of high brightness, i.e. intensity to emittance ratio, all along the injector chain. Amongst the phenomena that can blow up and even destroy the beam are transverse coherent instabilities. Two methods are widely used to damp these instabilities. The first one is Landau damping by non-linearities. The second consists in using an electronic feedback system. However, non-linearities are harmful to single-particle motion due to resonance phenomena, and powerful wideband feedback systems are expensive. It is shown in this paper that linear coupling is a further method that can be used to damp transverse coherent instabilities. The theory of collective motion is outlined, including the coupling of instability rise and damping rates, chromaticity and Landau damping. Experimental results obtained at the CERN PS are reported, which are important for its role as LHC injector. Stabilisation by coupling explains (at least in part) why existing high intensity accelerators and colliders work best when adjusted relatively close to a coupling resonance. This method could be profitably used in the design of new machines
On the Standard Approach to Renormalization Group Improvement
Two approaches to renormalization-group improvement are examined: the
substitution of the solutions of running couplings, masses and fields into
perturbatively computed quantities is compared with the systematic sum of all
the leading log (LL), next-to-leading log (NLL) etc. contributions to
radiatively corrected processes, with n-loop expressions for the running
quantities being responsible for summing N^{n}LL contributions. A detailed
comparison of these procedures is made in the context of the effective
potential V in the 4-dimensional O(4) massless model,
showing the distinction between these procedures at two-loop order when
considering the NLL contributions to the effective potential V.Comment: 6 page
Physical and Spectral Characteristics of the T8 and Later-Type Dwarfs
We use new and published near-IR spectra, with synthetic spectra, to derive
physical properties of three of the latest-type T dwarfs. A new R~1700 spectrum
of the T7.5 dwarf HD 3651B, with existing data, allows a detailed comparison to
the well-studied and very similar dwarf, Gl 570D. We find that HD 3651B has
both higher gravity and metallicity than Gl 570D, with Teff=820-830K, log g=
5.4-5.5, [m/H]= +0.2 and Kzz=10^4cm^2/s. Its age is 8-12 Gyr and its implied
mass is 60-70 M_Jup. We perform a similar analyis of the T8 and T7.5 dwarfs
2MASS J09393548-2448279 and 2MASS J11145133-2618235 using published data,
comparing them to the well-studied T8, 2MASS J04151954-0935066. We find that
the two dwarfs have the same Teff as the reference dwarf, and similar
gravities, but lower metallicities. The parameters are Teff=725-775K and [m/H]=
-0.3; log g=5.3-5.45 for 2MASS J09393548-2448279 and log g=5.0-5.3 for 2MASS
J11145133- 261823. The age and mass are ~10Gyr and 60M_Jup for 2MASS
J09393548-2448279, and ~5 Gyr and 40M_Jup for 2MASS J11145133-261823. A serious
limitation is the incompleteness of the line lists of CH4 and NH3 at lambda
<1.7um. Spectra of Saturn and Jupiter, and of laboratory CH4 and NH3 gas,
suggest that NH3 features in the Y- and J-bands may be useful as indicators of
the next cooler spectral type, and not features in the H- and K-bands as
previously thought. However large uncertainties remain, as the abundance of NH3
is likely to be significantly below the chemical equilibrium value, and
inclusion of laboratory NH3 opacities predicts band shapes that are discrepant
with existing data. It is possible that the T spectral class will have to be
extended to low temperatures around 400K, when water clouds condense in the
atmosphere [abridged].Comment: 34 pages including 10 figures and two tables; accepted for
publication in the Astrophysical Journa
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