Photonic processes in Born–Infeld theory

We study the processes of photon–photon scattering and photon splitting in a magnetic field in Born–Infeld theory. In both cases we combine the terms from the tree-level Born–Infeld Lagrangian with the usual one-loop QED contributions, where those are approximated by the Euler–Heisenberg Lagrangian, including also the interference terms. For photon–photon scattering we obtain the total cross-section in the low-energy approximation. For photon splitting we compute the total absorption coefficient in the hexagon (weak field) approximation, and also show that, due to the non-birefringence property of Born–Infeld theory, the selection rules found by Adler for the QED case continue to hold in this more general setting. We discuss the bounds on the free parameter of Born–Infeld theory that may be obtained from this type of processes.

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EXPLORING QUANTUM VACUUM WITH LOW-ENERGY PHOTONS

International Journal of Quantum Information ◽

10.1142/s021974991241002x ◽

2012 ◽

Vol 10 (08) ◽

pp. 1241002 ◽

Cited By ~ 11

Author(s):

E. MILOTTI ◽

F. DELLA VALLE ◽

G. ZAVATTINI ◽

G. MESSINEO ◽

U. GASTALDI ◽

...

Keyword(s):

Cross Section ◽

Gamma Rays ◽

Quantum Electrodynamics ◽

Low Energy ◽

Quantum Field ◽

Quantum Vacuum ◽

Vacuum Fluctuations ◽

Photon Scattering ◽

Electronic Field ◽

Photon Cross Section

Although quantum mechanics (QM) and quantum field theory (QFT) are highly successful, the seemingly simplest state — vacuum — remains mysterious. While the LHC experiments are expected to clarify basic questions on the structure of QFT vacuum, much can still be done at lower energies as well. For instance, experiments like PVLAS try to reach extremely high sensitivities, in their attempt to observe the effects of the interaction of visible or near-visible photons with intense magnetic fields — a process which becomes possible in quantum electrodynamics (QED) thanks to the vacuum fluctuations of the electronic field, and which is akin to photon–photon scattering. PVLAS is now close to data-taking and if it reaches the required sensitivity, it could provide important information on QED vacuum. PVLAS and other similar experiments face great challenges as they try to measure an extremely minute effect. However, raising the photon energy greatly increases the photon–photon cross section, and gamma rays could help extract much more information from the observed light–light scattering. Here we discuss an experimental design to measure photon–photon scattering close to the peak of the photon–photon cross section, that could fit in the proposed construction of an FEL facility at the Cabibbo Lab near Frascati (Rome, Italy).

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A p-Adic Matter in a Closed Universe

Symmetry ◽

10.3390/sym14010073 ◽

2022 ◽

Vol 14 (1) ◽

pp. 73

Author(s):

Branko Dragovich

Keyword(s):

Slight Modification ◽

Field Approximation ◽

Weak Field ◽

Einstein Gravity ◽

Tree Level ◽

Closed Universe ◽

Open Strings ◽

Weak Field Approximation ◽

New Type ◽

Nonlinear Lagrangian

In this paper, we introduce a new type of matter that has origin in p-adic strings, i.e., strings with a p-adic worldsheet. We investigate some properties of this p-adic matter, in particular its cosmological aspects. We start with crossing symmetric scattering amplitudes for p-adic open strings and related effective nonlocal and nonlinear Lagrangian which describes tachyon dynamics at the tree level. Then, we make a slight modification of this Lagrangian and obtain a new Lagrangian for non-tachyonic scalar field. Using this new Lagrangian in the weak field approximation as a matter in Einstein gravity with the cosmological constant, one obtains an exponentially expanding FLRW closed universe. At the end, we discuss the obtained results, i.e., computed mass of the scalar p-adic particle, estimated radius of related closed universe and noted p-adic matter as a possible candidate for dark matter.

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Remeasurement of the low-energy cross section for the reaction

Nuclear Physics A ◽

10.1016/0375-9474(79)90197-0 ◽

1979 ◽

Vol 320 (2) ◽

pp. 404-412 ◽

Cited By ~ 27

Author(s):

J.L. Zyskind ◽

P.D. Parker

Keyword(s):

Cross Section ◽

Low Energy

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Experiments on the reaction T( d , n ) 4 He I. The 90° cross-section

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1951.0005 ◽

1951 ◽

Vol 204 (1079) ◽

pp. 488-499 ◽

Cited By ~ 8

Keyword(s):

Cross Section ◽

Heavy Water ◽

Incident Beam ◽

Absolute Magnitude ◽

Alpha Particles ◽

Low Energy ◽

Energy Relation ◽

Conventional Theory ◽

Simultaneous Observation ◽

The Cross

The 90° cross-section of the reaction 3 1 H( d , n ) 4 2 He has been investigated over the energy range 100 to 200 keV (energy of bombarding triton) using the 200 keV accelerating set of the establishment. Two methods have been used. As a preliminary experiment the yield of alpha-particles from a thick heavy-ice target was measured per unit charge of incident beam, as a function of deuteron energy, and the variation of cross-section deduced from the gradient of this excitation curve and the range energy relation for tritons in heavy water. Secondly, a comparison was made between the yield of alpha-particles from the D-T reaction and the yield of protons from the D-D reaction when a beam containing both deuterons and tritons was passed through a heavy-water vapour target. (The energy loss in this target was calculated as only a few hundred electron volts.) To do this a simultaneous observation was made of the protons and alpha-particles using the same counter. The values obtained for the cross-section have been compared with the resonance formulae given by Bretscher & French (1949) and by Tascbek, Everhart, Gittings, Hemmendinger & Jarvis (1948) and have been found to be in disagreement with formulae of this type. From considerations of the absolute magnitude of the cross-section it has been deduced that no conventional theory postulating reaction at a distance equal to the sum of the nuclear radii (cf. Konopinski & Teller 1948) will be able to explain this reaction. The evidence for a low-energy resonance (Allan & Poole 1949) is thought to be inconclusive.

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The Einstein–Maxwell-particle system in the York canonical basis of ADM tetrad gravity. Part 2. The weak field approximation in the 3-orthogonal gauges and Hamiltonian post-minkowskian gravity: the N-body problem and gravitational waves with asymptotic background 1This paper is one of three companion papers published in the same issue of Can. J. Phys.

Canadian Journal of Physics ◽

10.1139/p11-101 ◽

2012 ◽

Vol 90 (11) ◽

pp. 1077-1130 ◽

Cited By ~ 11

Author(s):

David Alba ◽

Luca Lusanna

Keyword(s):

Electromagnetic Field ◽

Gravitational Waves ◽

Particle System ◽

Canonical Basis ◽

Field Approximation ◽

Weak Field ◽

N Body Problem ◽

Hamilton Equations ◽

Weak Field Approximation ◽

Tetrad Gravity

In this second paper we define a post-minkowskian (PM) weak field approximation leading to a linearization of the Hamilton equations of Arnowitt–Deser–Misner (ADM) tetrad gravity in the York canonical basis in a family of nonharmonic 3-orthogonal Schwinger time gauges. The York time 3K (the relativistic inertial gauge variable, not existing in newtonian gravity, parametrizing the family, and connected to the freedom in clock synchronization, i.e., to the definition of the the shape of the instantaneous 3-spaces) is set equal to an arbitrary numerical function. The matter are considered point particles, with a Grassmann regularization of self-energies, and the electromagnetic field in the radiation gauge: an ultraviolet cutoff allows a consistent linearization, which is shown to be the lowest order of a hamiltonian PM expansion. We solve the constraints and the Hamilton equations for the tidal variables and we find PM gravitational waves with asymptotic background (and the correct quadrupole emission formula) propagating on dynamically determined non-euclidean 3-spaces. The conserved ADM energy and the Grassmann regularization of self-energies imply the correct energy balance. A generalized transverse–traceless gauge can be identified and the main tools for the detection of gravitational waves are reproduced in these nonharmonic gauges. In conclusion, we get a PM solution for the gravitational field and we identify a class of PM Einstein space–times, which will be studied in more detail in a third paper together with the PM equations of motion for the particles and their post-newtonian expansion (but in the absence of the electromagnetic field). Finally we make a discussion on the gauge problem in general relativity to understand which type of experimental observations may lead to a preferred choice for the inertial gauge variable 3K in PM space–times. In the third paper we will show that this choice is connected with the problem of dark matter.

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