Search results for "electrodynamics"
showing 10 items of 820 documents
Quantum control and long-range quantum correlations in dynamical Casimir arrays
2015
The recent observation of the dynamical Casimir effect in a modulated superconducting waveguide, coronating thirty years of world-wide research, empowered the quantum technology community with a powerful tool to create entangled photons on-chip. In this work we show how, going beyond the single waveguide paradigm using a scalable array, it is possible to create multipartite nonclassical states, with the possibility to control the long-range quantum correlations of the emitted photons. In particular, our finite-temperature theory shows how maximally entangled $NOON$ states can be engineered in a realistic setup. The results here presented open the way to new kinds of quantum fluids of light,…
Finite-size scaling in Ising-like systems with quenched random fields: Evidence of hyperscaling violation
2010
In systems belonging to the universality class of the random field Ising model, the standard hyperscaling relation between critical exponents does not hold, but is replaced by a modified hyperscaling relation. As a result, standard formulations of finite size scaling near critical points break down. In this work, the consequences of modified hyperscaling are analyzed in detail. The most striking outcome is that the free energy cost \Delta F of interface formation at the critical point is no longer a universal constant, but instead increases as a power law with system size, \Delta F proportional to $L^\theta$, with $\theta$ the violation of hyperscaling critical exponent, and L the linear ex…
Is massless quantum electrodynamics a free-field theory?
1976
It is shown that if the photon wave-function renormalization constant is finite, then in the limit of zero fermion mass, quantum electrodynamics is a free- field theory.
Considerations concerning the renormalization of the electroweak sector of the standard model
1990
Abstract Examination of the structure of one-loop corrected amplitudes for arbitrary processes mediated by W, Z and γ in the simple renormalization framework previously discussed by the author, leads to natural choices for the renormalized self-energies and vertex corrections. They satisfy simple renormalization conditions and, as q2 → 0, the W and Z propagators approach the free expressions with a correction of O(αq2/mW2). The renormalization conditions allow us to circumvent certain ambiguities that arise, to O(α2), in current analyses of Δr and κ(q2). A useful simplified form for the Z propagator is presented.
Radiative Improvement of the Lattice Nonrelativistic QCD Action Using the Background Field Method and Application to the Hyperfine Splitting of Quark…
2011
We present the first application of the background field method to nonrelativistic QCD (NRQCD) on the lattice in order to determine the one-loop radiative corrections to the coefficients of the NRQCD action in a manifestly gauge-covariant manner. The coefficients of the $\mathbit{\ensuremath{\sigma}}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{B}$ term in the NRQCD action and the four-fermion spin-spin interaction are computed at the one-loop level; the resulting shift of the hyperfine splitting of bottomonium is found to bring the lattice predictions in line with experiment.
Scattering amplitudes and integral equations for the collision of two charged composite particles
1980
Transition operators for the collision of two clusters composed of an arbitrary number of charged and neutral particles are represented as a sum of pure Coulomb and Coulomb-modified short-range operators. Sandwiching this relation between the corresponding channel states, correct two-fragment scattering amplitudes are obtained by adapting the conventional two-body screening and renormalization procedure. Furthermore, integral equations are derived for off-shell extensions of the full screened amplitudes and of the unscreened Coulomb-modified short-range amplitudes. For three particles, the final results coincide with those derived previously in a different approach. The proposed theory is v…
Coulomb Effects on Few-Body Scattering States
1986
Modifications of stationary momentum space scattering theory, necessitated by the presence of Coulomb forces, are described, both in the formalism which uses unscreened Coulomb potentials and in the screening and renormalization approach. Thereby, emphasis is laid on exposing the conceptual differences, as well as the different, presently achieved status of applicability. Some of the unresolved problems in both methods are enumerated.
Bag Scattering Theory
1986
We reanalyze the procedure used thus far for the study of collision processes in the Chiral Bag Model from the point of view of scattering theory. In the present formalism thein andout states are free waves with no memory of the cavity. This feature gives rise to an observable effect consisting in a peculiar momentum dependence of the scattering amplitudes, which differs from that of previous calculations. The new procedure however does not change the magnitude of the pion-baryon coupling constants.
Potentials with SuppressedS-Wave Phase Shift at Low Energies
1972
These results are valid for arbitrary range and depths of the potentials here studied. In spite of the fact that for the general solution we have worked only with a particular radial dependence, for .which an explicit solution for the phase shifts can be written down, it seems plausible that the results have a more general validity. With this generalization in mind, we show that for general shapes of the radial dependence, the phase shifts in Born approximation present the momentum dependence described above. The origin of our results become transparent in this Born approximation treatment. We consider a velocity dependent potential of the form 1 )
Time-dependent ground-state correlations in heavy ion scattering
1982
Using a time-dependent generator-coordinate method, we derive a theory for time-dependent collective ground-state correlations which account for some quantum fluctuations about a TDHF trajectory. This theory is particularly suited for evaluating spreading widths of collective one-body operators. As an application we study head-on collision of heavy ions in a one-dimensional model. As one of the prominent results we find a substantial enhancement of the spreading width of the internal excitation energy due to the correlations.