The emission of e+ e- pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g., laser) wave field is analyzed. A significant increase of the total cross section of ...pair production in the subthreshold region is found for decreasing laser pulse duration even in the case of moderate laser pulse intensities.
The probabilities of various elementary laser-photon-electron/positron interactions display in selected phase space and parameter regions typical nonperturbative dependencies such as ... where P is a ...preexponential factor, Ecrit denotes the critical Sauter-Schwinger field strength, and E characterizes the (laser) field strength. While the Schwinger process with a = aS ≡ π and the nonlinear Breit-Wheeler process in the tunneling regime with ... (with ω ′ the probe photon energy and m the electron/positron mass) are famous results, we point out here that also the nonlinear Compton scattering exhibits a similar behavior when focusing on high harmonics. Using a suitable cutoff c > 0, the factor a becomes ... This opens the avenue toward a new signature of the boiling point of the vacuum even for field strengths E below E crit by employing a high electron beam-energy p0 to counter balance the large ratio Ecrit/E by a small factor a to achieve E/a → Ecrit. In the weak-field regime, the cutoff facilitates a threshold leading to multiphoton signatures showing up in the total cross section at subthreshold energies.(ProQuest: ... denotes formulae omitted.)
A dilaton potential is adjusted to recently confirmed lattice QCD thermodynamics data in the temperature range
(
0.7
…
3.5
)
T
c
where
T
c
=
155
MeV
is the pseudo-critical temperature. The employed ...holographic model is based on a gravity–single-field dilaton dual. We discuss conditions for enforcing (for the pure gluon plasma) or avoiding (for the QCD quark–gluon plasma) a first-order phase transition, but still keeping a softest point (minimum of sound velocity).
.
We consider the vacuum decay by electron-positron pair production in spatially homogeneous, time-dependent electric fields by means of quantum kinetic equations. Our focus is on the impact of ...various pulse shapes as envelopes of oscillating fields and the assistance effects in multi-scale fields, which are also seen in photons accompanying the creation and motion of pairs.
The finite-temperature behavior of ghost and gluon propagators is investigated within an approach based on the rainbow truncated Dyson–Schwinger equations in Landau gauge. In Euclidean space, within ...the Matsubara imaginary-time formalism, the gluon propagator is no longer an
O
(4) symmetric function and possesses a discrete spectrum of the fourth momentum component. This leads to a different treatment of the transversal and longitudinal (with respect to the heat bath) parts of the propagator. Correspondingly, the gluon Dyson–Schwinger equation splits also into two parts. The resulting system of coupled equations is considered within the rainbow approximation and solved numerically. The solutions for the ghost and gluon propagators are obtained as functions of the temperature
T
, Matsubara frequency
and three-momentum squared
. The effective parameters of the approach are taken from our previous fit of the corresponding Dyson–Schwinger solution to the lattice QCD data at zero temperature. It is found that, for zero Matsubara frequency, the dependence of the ghost and gluon dressing functions on
are not sensitive to the temperature
T
, while at
their dependence on
T
is quite strong. Dependence on the Matsubara frequency
is investigated as well.
Asymptotic AdS Riemann space-times in five dimensions with a black brane (horizon) sourced by a fully back-reacted scalar field (dilaton) offer—via the holographic dictionary—various options for the ...thermodynamics of the flat four-dimensional boundary theory, uncovering Hawking–Page, first-order, and second-order phase transitions up to a cross-over or featureless behavior. The relation of these phase structures to the dilaton potential is clarified and illustrating examples are presented. Having in mind applications to QCD, we study probe vector mesons with the goal to figure out conditions for forming Regge-type series of radial excitations and address the issue of meson melting.
Electron–positron pair production by the Breit–Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as ...caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering.
The e+e− pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit–Wheeler process. For short laser pulses with very few oscillations of ...the electromagnetic field we find below the perturbative weak-field threshold s=2m a similar enhancement of the pair production rate as for circular polarization. The strong enhancement below the weak-field threshold is traced back to the finite bandwidth of the laser pulse. A folding model is developed which accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.
.
The soft wall model is extended to accommodate at the same time i) approximately linear
ρ
meson Regge trajectories at zero temperature
T
, ii) various options for the thermodynamics with reference ...to QCD (cross-over or second-order transition or first-order transition at
T
c
, and iii) the appearance of vector meson states at
T
≲
T
c
. While the vector meson masses display some modest model dependence very near to
T
c
, they stay below
T
c
to good accuracy independent of the temperature, that is nearly as at
T
=
0
, thus being very consistent with the thermo-statistical models widely employed in analyses of the hadron yields in relativistic heavy-ion collisions in a region where baryon densitiy effects can be neglected and the vacuum hadron masses are used.
We derive a new scaling law for the photon spectral density in nonlinear Thomson/Compton scattering, extending the findings of Heinzl, Seipt, and Kämpfer Phys. Rev. A 81, 022125 (2010). This allows ...one to easily include the effects of general scattering geometries, e.g., side injection, and of a finite-size detector on the photon spectrum. The scaling law is employed to study substructures emerging in the nonlinear Thomson/Compton spectra due to temporally shaped laser pulses scattering off relativistic electrons. We determine optimum scattering geometries for an experimental verification of these substructures.
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