Photon location in spacetime

The NewtonWigner basis of orthonormal localized states is generalized to orthonormal and relativistic biorthonormal bases on an arbitrary hyperplane in spacetime. This covariant formalism is applied to the measurement of photon location using a hypothetical 3D array with pixels throughout space turned on at a fixed time and a timelike 2D photon counting array detector with good time resolution. A moving observer will see these detector arrays as rotated in spacetime but the spacelike and timelike experiments remain distinct.Comment: Equations (18) to (21) and the relevant text deleted due to an error in (20). This is no effect on the conclusions of the pape

Quantum field theory and classical optics: determining the fine structure constant

The properties of the vacuum are described by quantum physics including the response to external fields such as electromagnetic radiation. Of the two parameters that govern the details of the electromagnetic field dynamics in vacuum, one is fixed by the requirement of Lorentz invariance $c= 1/\sqrt{\varepsilon_{0} \mu_{0}}$. The other one, $Z_{0}= \sqrt{\mu_{0}/\varepsilon_{0}} = 1/(c\varepsilon_{0})$ and its relation to the quantum vacuum, is discussed in this contribution. Deriving $\varepsilon_{0}$ from the properties of the quantum vacuum implies the derivation of the fine structure constant.Comment: 3 pages. Invited contribution to MPLP 2017 Novosibirsk "Modern Problems in Laser Physics". Comments welcome

Photon correlations in positron annihilation

The two-photon positron annihilation density matrix is found to separate into a diagonal center of energy factor implying maximally entangled momenta, and a relative factor describing decay. For unknown positron injection time, the distribution of the difference in photon arrival times is a double exponential at the para-Ps decay rate, consistent with experiment (V. D. Irby, Meas. Sci. Technol. 15, 1799 (2004)).Comment: Accepted for publication in Phys. Rev.

Physical mechanisms underpinning the vacuum permittivity

© 2023 by the authors. This research was funded by the Spanish Ministerio de Ciencia e Innovación (Grant PGC2018-099183-B-I00).The debate about the emptiness of space goes back to the prehistory of science and is epitomized by the Aristotelian 'horror vacui', which can be seen as the precursor of the ether, whose modern version is the dynamical quantum vacuum. In this paper, we suggest to change a common view to 'gaudium vacui' and discuss how the vacuum fluctuations fix the value of the permittivity, e(0), and permeability, mu(0), by modelling their dynamical response by three-dimensional harmonic oscillators.Depto. de ÓpticaFac. de Ciencias FísicasTRUEMinisterio de Ciencia e Innovación (MICINN)pu