1,993 research outputs found
Gauge invariance, background fields and modified Ward identities
In this talk the gauge symmetry for Wilsonian flows in pure Yang-Mills
theories is discussed. The background field formalism is used for the
construction of a gauge invariant effective action. The symmetries of the
effective action under gauge transformations for both the gauge field and the
auxiliary background field are separately evaluated. Modified Ward-Takahashi
and background field identities are used in my study. Finally it is shown how
the symmetry properties of the full theory are restored in the limit where the
cut-off is removed.Comment: 6 pages, to appear in the Proceedings of the 2nd Conference on the
Exact Renormalization Group, Rome 200
Uniqueness of infrared asymptotics in Landau gauge Yang-Mills theory
We uniquely determine the infrared asymptotics of Green functions in Landau
gauge Yang-Mills theory. They have to satisfy both,
Dyson-Schwinger equations and functional renormalisation group equations.
Then, consistency fixes the relation between the infrared power laws of these
Green functions. We discuss consequences for the interpretation of recent
results from lattice QCD.Comment: 24 pages, 8 figure
Method and apparatus for receiving and tracking phase modulated signals
An apparatus and technique are described for receiving and tracking analog or digital phase modulated signals from 0 deg to 360 deg phase shift. In order to track a signal with many phases, a detector discerns the phase modulation of the incoming signal and a phase shifter generates a negative phase shift opposite in angle to the detected phase angle. This produces a converted series sideband component barrier signal. The residual carrier signal and the converted series sideband component carrier are added together to produce a tracking carrier signal. The tracking carrier signal is multiplied with the output from a voltage controlled oscillator in the tracking loop to obtain an error signal which drives the voltage controlled oscillator and tracks the incoming signal frequency. The technique is less susceptible to carrier interference which may degrade tracking and tracking may be performed at lower signal to noise ratios and for lower input signal power levels
Sensitivity analysis of the probabilistic damage stability regulations for RoPax vessels
In the light of the newly developed harmonised probabilistic damage stability regulations, set to come into force in 2009, this article presents a systematic and thorough analysis of the sensitivity of the Attained Subdivision Index with reference to a wide range of related design parameters. The sensitivity of the probabilistic regulations was investigated for a typical large RoPax vessel, with variation of parameters, such as the number, positioning and local optimisation of transverse bulkheads; the presence and position of longitudinal bulkheads below the main vehicle deck; the presence of side casings; and the height of the main deck and double bottom. The effects of water on deck and of operational parameters (draught, centre of gravity and trim) were also investigated. The results of the study, presented in graphical form, can provide valuable assistance to the designer when determining subdivision characteristics at the very early stage of the design process, resulting in optimal, efficient and safe ships
Signatures of confinement in Landau gauge QCD
We summarise an analysis of the infrared regime of Landau gauge QCD by means
of a flow equation approach. The infrared behaviour of gluon and ghost
propagators is evaluated. The results provide further evidence for the
Kugo-Ojima confinement scenario. We also discuss their relation to results
obtained with other functional methods as well as the lattice.Comment: 3 pages, talk given by JMP at 6th Conference on Quark Confinement and
the Hadron Spectrum, Villasimius, Sardinia, Italy, 21-25 Sep 200
Consuming Bits: An Exploratory Study of User Goals for Virtual Consumption
Virtual consumption, or consumption of virtual goods and property, has become a major economic activity in social virtual worlds such as Second Life. Given that virtual consumption has become an important part of everyday virtual life in social virtual worlds, understanding virtual consumption can be an essential aspect to understanding user behavior in those worlds. Despite its significance, little research has explicitly examined virtual consumption. Unsurprisingly, then, we know very little concerning the fundamental question of why users consume virtual property. The research study described in this paper is an initial examination of that question. For the study, we employed the laddering interview technique and means-end chain analysis, which produces usersâ goal structure in reference to a hierarchical system of interrelated goals. 93 participants were interviewed in Second Life for the study. The results show that virtual consumption widely penetrates into virtual life and make virtual experience much richer
Cosmological Symmetry Breaking, Pseudo-scale invariance, Dark Energy and the Standard Model
The energy density of the universe today may be dominated by the vacuum
energy of a slowly rolling scalar field. Making a quantum expansion around such
a time dependent solution is found to break fundamental symmetries of quantum
field theory. We call this mechanism cosmological symmetry breaking and argue
that it is different from the standard phenomenon of spontaneous symmetry
breaking. We illustrate this with a toy scalar field theory, whose action
displays a U(1) symmetry. We identify a symmetry, called pseudo-scale
invariance, which sets the cosmological constant exactly equal to zero, both in
classical and quantum theory. This symmetry is also broken cosmologically and
leads to a nonzero vacuum or dark energy. The slow roll condition along with
the observed value of dark energy leads to a value of the background scalar
field of the order of Planck mass. We also consider a U(1) gauge symmetry
model. Cosmological symmetry breaking, in this case, leads to a non zero mass
for the vector field. We also show that a cosmologically broken pseudo-scale
invariance can generate a wide range of masses.Comment: 18 pages, no figure
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