6,624 research outputs found

    Explicit expression for the photon number emission in synchrotron radiation

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    An explicit and remarkably simple one-dimensional integral expression is derived for the mean number of photons emitted per revolution in synchrotron radiation. The familiar high-energy expression $5\pi\alpha/\sqrt{3(1-\beta^2)}$, printed repeatedly in the literature, is found to be inaccurate and only truly asymptotic with relative errors of 160%, 82% for $\beta=0.8$, 0.9, respectively. A new improved high-energy expression for is given.Comment: LaTeX, 3 pages, no figur

    Sonoluminescence: Bogolubov coefficients for the QED vacuum of a time-dependent dielectric bubble

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    We extend Schwinger's ideas regarding sonoluminescence by explicitly calculating the Bogolubov coefficients relating the QED vacuum states associated with changes in a dielectric bubble. Sudden (non-adiabatic) changes in the refractive index lead to an efficient production of real photons with a broadband spectrum, and a high-frequency cutoff that arises from the asymptotic behaviour of the dielectric constant.Comment: 4 pages, RevTeX, 2 figures (.eps file) included with graphics.sty. Major revisions: physical scenario clarified, additional numerical estimate

    Casimir energy of dielectric systems

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    A new formula for the Casimir energy of a dispersive dilute dielectric ball is discussed. The formula for the Casimir energy of a polarizable particle situated in a perfectly conducting wedge-shaped cavity is derived by a path-integral coordinate space method in quantum field theory.Comment: Latex 2e, 4 pages, no figures, a talk given at the International Meeting "Quantum Gravity and Spectral Geometry" (Naples, Italy, July 2-7, 2001

    Functional treatment of quantum scattering via the dynamical principle

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    A careful functional treatment of quantum scattering is given using Schwinger's dynamical principle which involves a functional differentiation operation applied to a generating functional written in closed form. For long range interactions, such as for the Coulomb one, it is shown that this expression may be used to obtain explicitly the asymptotic "free" modified Green function near the energy shell.Comment: 7 page

    Quantum Corrections to Synchrotron Radiation from Wave-Packet

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    We calculate the radiated energy to O(ℏ)O(\hbar) from a charged wave-packet in the uniform magnetic field. In the high-speed and weak-field limit, while the non-commutativity of the system reduces the classical radiation, the additional corrections originated from the velocity uncertainty of the wave-packet leads to an enhancement of the radiation.Comment: 7 pages, no figur

    Schwinger's Dynamical Casimir Effect: Bulk Energy Contribution

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    Schwinger's Dynamical Casimir Effect is one of several candidate explanations for sonoluminescence. Recently, several papers have claimed that Schwinger's estimate of the Casimir energy involved is grossly inaccurate. In this letter, we show that these calculations omit the crucial volume term. When the missing term is correctly included one finds full agreement with Schwinger's result for the Dynamical Casimir Effect. We have nothing new to say about sonoluminescence itself except to affirm that the Casimir effect is energetically adequate as a candidate explanation.Comment: 6 pages. Uses LaTeX with RevTeX package in two-column forma

    Sonoluminescence as a QED vacuum effect. II: Finite Volume Effects

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    In a companion paper [quant-ph/9904013] we have investigated several variations of Schwinger's proposed mechanism for sonoluminescence. We demonstrated that any realistic version of Schwinger's mechanism must depend on extremely rapid (femtosecond) changes in refractive index, and discussed ways in which this might be physically plausible. To keep that discussion tractable, the technical computations in that paper were limited to the case of a homogeneous dielectric medium. In this paper we investigate the additional complications introduced by finite-volume effects. The basic physical scenario remains the same, but we now deal with finite spherical bubbles, and so must decompose the electromagnetic field into Spherical Harmonics and Bessel functions. We demonstrate how to set up the formalism for calculating Bogolubov coefficients in the sudden approximation, and show that we qualitatively retain the results previously obtained using the homogeneous-dielectric (infinite volume) approximation.Comment: 23 pages, LaTeX 209, ReV-TeX 3.2, five figure

    Relativistic, Causal Description of Quantum Entanglement and Gravity

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    A possible solution to the problem of providing a spacetime description of the transmission of signals for quantum entangled states is obtained by using a bimetric spacetime structure, in which quantum entanglement measurements alter the structure of the classical relativity spacetime. A bimetric gravity theory locally has two lightcones, one which describes classical special relativity and a larger lightcone which allows light signals to communicate quantum information between entangled states, after a measurement device detects one of the entangled states. The theory would remove the tension that exists between macroscopic classical, local gravity and macroscopic nonlocal quantum mechanics.Comment: 12 pages. LaTex file. 1 figure. Additional text. To be published in Int. J. Mod. Phys.

    Generally covariant quantization and the Dirac field

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    Canonical Hamiltonian field theory in curved spacetime is formulated in a manifestly covariant way. Second quantization is achieved invoking a correspondence principle between the Poisson bracket of classical fields and the commutator of the corresponding quantum operators. The Dirac theory is investigated and it is shown that, in contrast to the case of bosonic fields, in curved spacetime, the field momentum does not coincide with the generators of spacetime translations. The reason is traced back to the presence of second class constraints occurring in Dirac theory. Further, it is shown that the modification of the Dirac Lagrangian by a surface term leads to a momentum transfer between the Dirac field and the gravitational background field, resulting in a theory that is free of constraints, but not manifestly hermitian.Comment: final version, to appear in Annals Phy