563 research outputs found
Algebraic characterization of constraints and generation of mass in gauge theories
The possibility of non-trivial representations of the gauge group on
wavefunctionals of a gauge invariant quantum field theory leads to a generation
of mass for intermediate vector and tensor bosons. The mass parameters "m" show
up as central charges in the algebra of constraints, which then become of
second-class nature. The gauge group coordinates acquire dynamics outside the
null-mass shell and provide the longitudinal field degrees of freedom that
massless bosons need to form massive bosons.Comment: 4 pages, LaTeX, no figures; uses espcrc2.sty (twocolumn).
Contribution to the "Third Meeting on Constrained Dynamics and Quantum
Gravity QG99" held in Sardinia, Italy, on Sept. 1999. To appear in Nucl.
Phys. B (Proc. Suppl.
Quantumness in decoherent quantum walk using measurement-induced disturbance
The classicalization of a decoherent discrete-time quantum walk on a line or
an n-cycle can be demonstrated in various ways that do not necessarily provide
a geometry-independent description. For example, the position probability
distribution becomes increasingly Gaussian, with a concomitant fall in the
standard deviation, in the former case, but not in the latter. As another
example, each step of the quantum walk on a line may be subjected to an
arbitrary phase gate, without affecting the position probability distribution,
no matter whether the walk is noiseless or noisy. This symmetry, which is
absent in the case of noiseless cyclic walk, but is restored in the presence of
sufficient noise, serves as an indicator of classicalization, but only in the
cyclic case. Here we show that the degree of quantum correlations between the
coin and position degrees of freedom, quantified by a measure based on the
disturbance induced by local measurements (Luo, Phys. Rev. A 77, 022301
(2008)), provides a suitable measure of classicalization across both type of
walks. Applying this measure to compare the two walks, we find that cyclic
quantum walks tend to classicalize faster than quantum walks on a line because
of more efficient phase randomization due to the self-interference of the two
counter-rotating waves. We model noise as acting on the coin, and given by the
squeezed generalized amplitude damping (SGAD) channel, which generalizes the
generalized amplitude damping channel.Comment: 8 pages with 8 figures, Published versio
The relationships between health anxiety, online health information seeking, and cyberchondria: Systematic review and meta-analysis
© 2018 Background: Cyberchondria refers to an abnormal behavioral pattern in which excessive or repeated online searches for health-related information are distressing or anxiety-provoking. Health anxiety has been found to be associated with both online health information seeking and cyberchondria. The aims of the present systematic review and meta-analysis were to examine the magnitude of these associations and identify any moderator variables. Methods: A systematic literature search was performed across several databases (PsycINFO, PubMed, Embase) and reference lists of included studies. Results: Twenty studies were included across two independent meta-analyses, with 7373 participants. Random effects meta-analyses showed that there was a positive correlation between health anxiety and online health information seeking [r = 0.34, 95% CI (0.20, 0.48), p <.0001], and between health anxiety and cyberchondria [r = 0.62, 95% CI (0.52, 0.71), p <.0001]. A meta-regression indicated that the age of study participants [Q(1) = 4.58, p =.03] was partly responsible for the heterogeneity found for the relationship between health anxiety and cyberchondria. Limitations: The generalizability and validity of our findings are restricted by the methodological limitations of the primary studies, namely, an over-reliance on a single measure of cyberchondria, the Cyberchondria Severity Scale. Conclusions: Our review found a positive correlation between health anxiety and online health information seeking, and between health anxiety and cyberchondria. Further research should aim to explore the contexts for these associations as well as address the identified limitations of the extant literature
Electrons in an eccentric background field
We present a description of electrons propagating in an elliptically polarized, plane wave background which includes circular and linear polarizations as special cases. We calculate, to all orders in the background field, the two point function and relate it to various expressions found in the literature. The background field induced mass shift of the electron is shown to be polarization independent in the full elliptic class. The matrix nature of this mass shift in the fermionic theory is discussed. The extent to which a momentum space description is possible for this system is clarified
Maintaining the quality of Western Australia\u27s oat harvest
WESTERN AUSTRALIA deservedly enjoys the reputation of being a producer of oats of high milling quality.
Because of this, we have been able to develop valuable export markets which pay a premium for our oats.
For some time Ballidu has been rated as the best milling oat in W.A.
The work reported in this article indicates that other recommended varieties are equal to or better than Ballidu for milling
BRST operator quantization of generally covariant gauge systems
The BRST generator is realized as a Hermitian nilpotent operator for a
finite-dimensional gauge system featuring a quadratic super-Hamiltonian and
linear supermomentum constraints. As a result, the emerging ordering for the
Hamiltonian constraint is not trivial, because the potential must enter the
kinetic term in order to obtain a quantization invariant under scaling. Namely,
BRST quantization does not lead to the curvature term used in the literature as
a means to get that invariance. The inclusion of the potential in the kinetic
term, far from being unnatural, is beautifully justified in light of the
Jacobi's principle.Comment: 16 pages (LaTeX manuscript). Revised version (minor changes) to
appear in Physical Review
The ice-limit of Coulomb gauge Yang-Mills theory
In this paper we describe gauge invariant multi-quark states generalising the
path integral framework developed by Parrinello, Jona-Lasinio and Zwanziger to
amend the Faddeev-Popov approach. This allows us to produce states such that,
in a limit which we call the ice-limit, fermions are dressed with glue
exclusively from the fundamental modular region associated with Coulomb gauge.
The limit can be taken analytically without difficulties, avoiding the Gribov
problem. This is llustrated by an unambiguous construction of gauge invariant
mesonic states for which we simulate the static quark--antiquark potential.Comment: 25 pages, 4 figure
Hodge Duality Operation And Its Physical Applications On Supermanifolds
An appropriate definition of the Hodge duality operation on any
arbitrary dimensional supermanifold has been a long-standing problem. We define
a working rule for the Hodge duality operation on the -dimensional supermanifold parametrized by a couple of even (bosonic)
spacetime variables and a couple of Grassmannian (odd)
variables and of the Grassmann algebra. The Minkowski
spacetime manifold, hidden in the supermanifold and parametrized by , is chosen to be a flat manifold on which a two -dimensional
(2D) free Abelian gauge theory, taken as a prototype field theoretical model,
is defined. We demonstrate the applications of the above definition (and its
further generalization) for the discussion of the (anti-)co-BRST symmetries
that exist for the field theoretical models of 2D- (and 4D) free Abelian gauge
theories considered on the four - (and six )-dimensional
supermanifolds, respectively.Comment: LaTeX file, 25 pages, Journal-versio
Reply to Comment hep-th/9509028
This is a reply to the above comment (hep-th/9509028). We argue that QED
displays a class of symmetries which may be used to select out the various
velocity dependent superselection sectors.Comment: 2 pages, plain Te
Probing the ground state in gauge theories
We consider two very different models of the flux tube linking two heavy
quarks: a string linking the matter fields and a Coulombic description of two
separately gauge invariant charges. We compare how close they are to the
unknown true ground state in compact U(1) and the SU(2) Higgs model.
Simulations in compact U(1) show that the string description is better in the
confined phase but the Coulombic description is best in the deconfined phase;
the last result is shown to agree with analytical calculations. Surprisingly in
the non-abelian theory the Coulombic description is better in both the Higgs
and confined phases. This indicates a significant difference in the width of
the flux tubes in the two theories.Comment: 13 pages, 10 .eps figures. V2: conclusions extende
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