365 research outputs found
Parametric Representation of Noncommutative Field Theory
In this paper we investigate the Schwinger parametric representation for the
Feynman amplitudes of the recently discovered renormalizable quantum
field theory on the Moyal non commutative space. This
representation involves new {\it hyperbolic} polynomials which are the
non-commutative analogs of the usual "Kirchoff" or "Symanzik" polynomials of
commutative field theory, but contain richer topological information.Comment: 31 pages,10 figure
Heavy-Higgs Lifetime at Two Loops
The Standard-Model Higgs boson with mass decays almost
exclusively to pairs of and bosons. We calculate the dominant two-loop
corrections of to the partial widths of these decays. In
the on-mass-shell renormalization scheme, the correction factor is found to be
, where the second term is the
one-loop correction. We give full analytic results for all divergent two-loop
Feynman diagrams. A subset of finite two-loop vertex diagrams is computed to
high precision using numerical techniques. We find agreement with a previous
numerical analysis. The above correction factor is also in line with a recent
lattice calculation.Comment: 26 pages, 6 postscript figures. The complete paper including figures
is also available via WWW at
http://www.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/TUM-HEP-247-96.ps.g
From Quantum Mechanics to Quantum Field Theory: The Hopf route
We show that the combinatorial numbers known as {\em Bell numbers} are
generic in quantum physics. This is because they arise in the procedure known
as {\em Normal ordering} of bosons, a procedure which is involved in the
evaluation of quantum functions such as the canonical partition function of
quantum statistical physics, {\it inter alia}. In fact, we shall show that an
evaluation of the non-interacting partition function for a single boson system
is identical to integrating the {\em exponential generating function} of the
Bell numbers, which is a device for encapsulating a combinatorial sequence in a
single function. We then introduce a remarkable equality, the Dobinski
relation, and use it to indicate why renormalisation is necessary in even the
simplest of perturbation expansions for a partition function. Finally we
introduce a global algebraic description of this simple model, giving a Hopf
algebra, which provides a starting point for extensions to more complex
physical systems
Operator approach to analytical evaluation of Feynman diagrams
The operator approach to analytical evaluation of multi-loop Feynman diagrams
is proposed. We show that the known analytical methods of evaluation of
massless Feynman integrals, such as the integration by parts method and the
method of "uniqueness" (which is based on the star-triangle relation), can be
drastically simplified by using this operator approach. To demonstrate the
advantages of the operator method of analytical evaluation of multi-loop
Feynman diagrams, we calculate ladder diagrams for the massless theory
(analytical results for these diagrams are expressed in terms of multiple
polylogarithms). It is shown how operator formalism can be applied to
calculation of certain massive Feynman diagrams and investigation of Lipatov
integrable chain model.Comment: 16 pages. To appear in "Physics of Atomic Nuclei" (Proceedings of
SYMPHYS-XII, Yerevan, Armenia, July 03-08, 2006
Holonomy of the Ising model form factors
We study the Ising model two-point diagonal correlation function by
presenting an exponential and form factor expansion in an integral
representation which differs from the known expansion of Wu, McCoy, Tracy and
Barouch. We extend this expansion, weighting, by powers of a variable
, the -particle contributions, . The corresponding
extension of the two-point diagonal correlation function, , is shown, for arbitrary , to be a solution of the sigma
form of the Painlev{\'e} VI equation introduced by Jimbo and Miwa. Linear
differential equations for the form factors are obtained and
shown to have both a ``Russian doll'' nesting, and a decomposition of the
differential operators as a direct sum of operators equivalent to symmetric
powers of the differential operator of the elliptic integral . Each is expressed polynomially in terms of the elliptic integrals and . The scaling limit of these differential operators breaks the
direct sum structure but not the ``Russian doll'' structure. The previous -extensions, are, for singled-out values ( integers), also solutions of linear differential
equations. These solutions of Painlev\'e VI are actually algebraic functions,
being associated with modular curves.Comment: 39 page
Parity Violating Gravitational Coupling Of Electromagnetic Fields
A manifestly gauge invariant formulation of the coupling of the Maxwell
theory with an Einstein Cartan geometry is given, where the space time torsion
originates from a massless Kalb-Ramond field augmented by suitable U(1) Chern
Simons terms.We focus on the situation where the torsion violates parity, and
relate it to earlier proposals for gravitational parity violation.Comment: 7 Pages, Latex . no figures, Replaced with Revtex version, many
references added and typos correcte
Two-Loop Diagrammatics in a Self-Dual Background
Diagrammatic rules are developed for simplifying two-loop QED diagrams with
propagators in a constant self-dual background field. This diagrammatic
analysis, using dimensional regularization, is used to explain how the fully
renormalized two-loop Euler-Heisenberg effective Lagrangian for QED in a
self-dual background field is naturally expressed in terms of one-loop
diagrams. The connection between the two-loop and one-loop vacuum diagrams in a
background field parallels a corresponding connection for free vacuum diagrams,
without a background field, which can be derived by simple algebraic
manipulations. It also mirrors similar behavior recently found for two-loop
amplitudes in N=4 SUSY Yang-Mills theory.Comment: 16 pp, Latex, Axodra
Efficacy and immunogenicity of a single dose of human papillomavirus vaccine compared to no vaccination or standard three and two-dose vaccination regimens: A systematic review of evidence from clinical trials.
OBJECTIVES: This study aimed to systematically review the literature on the efficacy and immunogenicity of single-dose HPV vaccination compared to no vaccination or multi-dose schedules among vaccine trial participants. METHODS: Medline, EMBASE, Global Health Database and Cochrane Central Register of Controlled Trials were searched for publications and conference abstracts (dated January 1999-August 2018) using MeSH and non-MeSH terms for human papillomavirus AND vaccines AND (immunogenicity OR efficacy/effectiveness) AND dosage. Search results were screened against pre-specified eligibility criteria. Data were extracted from included articles, and a narrative synthesis conducted on efficacy against HPV16/18 infection and humoral immunogenicity. RESULTS: Seven of 6,523 unique records identified were included in the review. Six were nested observational studies of participants randomised to receive two or three doses in three large HPV vaccine trials, in which some participants did not complete their allocated schedules. One small pilot study prospectively allocated participants to receive one or no vaccine dose. Frequency of HPV16/18 infection was low (e.g. 0.05 in all cases). Frequency of infection was significantly lower in one-dose recipients compared to unvaccinated controls (p < 0.01 for all infection endpoints in each study). HPV16/18 seropositivity rates were high in all HPV vaccine recipients (100% in three of four studies reporting this endpoint), though antibody levels were lower with one compared to two or three doses. CONCLUSIONS: This review supports the premise that one HPV vaccine dose may be as effective in preventing HPV infection as multi-dose schedules in healthy young women. However, it also highlights the paucity of available evidence from purpose-designed, prospectively-randomised trials. Results from ongoing clinical trials assessing the efficacy and immunogenicity of single-dose HPV vaccination compared to currently-recommended schedules are awaited
Hadronic light-by-light corrections to the muon g-2: the pion-pole contribution
The correction to the muon anomalous magnetic moment from the pion-pole
contribution to the hadronic light-by-light scattering is considered using a
description of the pi0 - gamma* - gamma* transition form factor based on the
large-Nc and short-distance properties of QCD. The resulting two-loop integrals
are treated by first performing the angular integration analytically, using the
method of Gegenbauer polynomials, followed by a numerical evaluation of the
remaining two-dimensional integration over the moduli of the Euclidean loop
momenta. The value obtained, a_{mu}(LbyL;pi0) = +5.8 (1.0) x 10^{-10},
disagrees with other recent calculations. In the case of the vector meson
dominance form factor, the result obtained by following the same procedure
reads a_{mu}(LbyL;pi0)_{VMD} = +5.6 x 10^{-10}, and differs only by its overall
sign from the value obtained by previous authors. Inclusion of the eta and
eta-prime poles gives a total value a_{mu}(LbyL;PS) = +8.3 (1.2) x 10^{-10} for
the three pseudoscalar states. This result substantially reduces the difference
between the experimental value of a_{mu} and its theoretical counterpart in the
standard model.Comment: 27 pages, Latex, 3 figures. v2: version to be published in Phys. Rev.
D, Note added and references updated (don't worry, sign has not changed
New Approach to GUTs
We introduce a new string-inspired approach to the subject of grand
unification which allows the GUT scale to be small, \lesssim 200 TeV, so that
it is within the reach of {\em conceivable} laboratory accelerated colliding
beam devices. The key ingredient is a novel use of the heterotic string
symmetry group physics ideas to render baryon number violating effects small
enough to have escaped detection to date. This part of the approach involves
new unknown parameters to be tested experimentally. A possible hint at the
existence of these new parameters may already exist in the EW precision data
comparisons with the SM expectations.Comment: 8 pages; improved text and references, note added; extended text, 1
figure added; extended text for publication in Eur. Phys. Journal
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