Probing the Photon Mass through the Electromagnetic Memory Effect

Yes, the photon. While a nonzero photon mass has been under experimental and theoretical study for years, the possible implication of a finite photon lifetime lacks discussion. The tight experimental upper bound of the photon mass restricts the kinematically allowed final states of photon decay to the lightest neutrino and/or particles beyond the standard model. We discuss the modifications of the well-measured cosmic microwave background spectrum of free streaming photons due to photon mass and lifetime and obtain model-independent constraints on both parameters--most importantly a lower direct bound of 3 yr on the photon lifetime, should the photon mass be at its conservative upper limit. In that case, the lifetime of microwave photons will be time-dilated by a factor order 10(15).

An exactly solvable model is used as a basis to study the reflectionless passage of a transverse electromagnetic wave through an inhomogeneous plasma containing large-amplitude, small-scale (subwave-length) structures (in particular, opaque regions) that cannot be correctly described by approximate methods. It is shown that, during the reflectionless passage of an electromagnetic wave, strong wave field splashes can occur in certain plasma sublayers. The nonuniform spatial plasma density profile is characterized by a number of free parameters describing the modulation depth of the dielectric function, the characteristic sizes of the structures and their number, the thickness of the inhomogeneous plasma region, and so on. Such plasma density structures are shown to be very diverse when, e.g., a wave that is incident from vacuum propagates without reflection through a plasma layer (wave barrier transillumination). With the cubic nonlinearity taken into account, a one-dimensional problem of the nonlinear transillumination of an inhomogeneous plasma can be solved exactly.

Space–time filling branes in non-critical (super) string theories

A conservative constraint on the rest mass of the photon can be estimated under the assumption that the frequency dependence of dispersion from astronomical sources is mainly contributed by the nonzero photon mass effect. Photon mass limits have been set earlier through the optical emissions of the Crab Nebula pulsar, but we demonstrate that these limits can be significantly improved with the dispersion measure (DM) measurements of radio pulsars in the Large and Small Magellanic Clouds. The combination of DM measurements of pulsars and distances of the Magellanic Clouds provides a strict upper limit on the photon mass as low as , which is at least four orders of magnitude smaller than the constraint from the Crab Nebula pulsar. Although our limit is not as tight as the current best result () from a fast radio burst (FRB 150418) at a cosmological distance, the cosmological origin of FRB 150418 remains under debate; and our limit can reach the same high precision of FRB 150418 when it has an extragalactic origin ().

Exploring the concept of a massive photon has been an important area in astronomy and physics. If photons have mass, their propagation in nonvacuum space would be affected by both the nonzero mass m γ and the presence of a plasma medium. This would lead to a delay time proportional to mγ2ν−4 , which deviates from the classical dispersion relation (proportional to ν −2). For the first time, we have derived the dispersion relation of a photon with a nonzero mass propagating in plasma. To reduce the impact of variations in the dispersion measure (DM), we employed the high-precision timing data to constrain the upper bound of the photon mass. Specifically, the DM/time of arrival (TOA) uncertainties derived from ultrawide bandwidth (UWB) observations conducted by the Parkes Pulsar Timing Array (PPTA) are used. The dedispersed pulses from fast radio bursts (FRBs) with minimal scattering effects are also used to constrain the upper bound of photon mass. The stringent limit on the photon mass is determined by uncertainties of the TOA of pulsars, with an optimum value of 9.52 × 10−46 kg (5.34 × 10−10 eV c−2). In the future, it is essential to investigate the photon mass, as pulsar timing data are collected by PPTA and UWB receivers, or FRBs with wideband spectra are detected by UWB receivers.

An aircraft in hypersonic flight regime is enveloped in a plasma layer due to the high temperatures involved. This electronic plasma layer will be responsible for cutting-off communications to and from the aircraft, in a phenomenon known as radio blackout. Several methods have been proposed to mitigate radio blackout, amongst which is the window. In the magnetic window method a magnetic field is imposed near the antenna, opening a spectral window, allowing the passage of electromagnetic waves without distortion. Experimental replication of hypersonic flight is extremely costly, generating a keen interest in the development of numerical codes capable of simulating weakly ionized flow around a hypersonic vehicle. This is specially relevant for investigating blackout mitigation methods, since a validated numerical code will allow the preliminary design and optimization of new concepts, in a much faster and cheaper way. A numerical code that is used to simulate a plasma layer around an aircraft needs to accurately predict the electron density and associated plasma properties. Several distinct chemistry models have been proposed. In this paper, four chemistry models will be studied, each accounting for 11 species commonly found in an atmospheric plasma layer: N2; O2; NO; N; O; N2+ ; O2+ ; NO+; N+; O+ and e−. The electron number density calculated with each model is compared with the electron number density calculated in the RAM-C II experimental flight. The models will be compared in terms of simulation runtime as well, in an attempt to assess which requires less processing power.

The solution of problems in the field of microwave electrotechnology related to mathematical modelling, development of installations or technology of electromagnetic field influence on the processing object requires knowledge of dielectric properties of high-energy radio-absorbing composites. The paper presents the results of computational and experimental study of dielectric properties of composite materials based on epoxy matrix with different absorbing fillers. Dielectric properties of materials were determined using the waveguide method based on the determination of the complex reflection coefficient and passage of electromagnetic waves through the working chamber with the investigated sample. By means of modelling the electric field strength distribution, the optimum geometry of the electromagnetic wave in the measuring microwave line (frequency — 2450 MHz) was found. It was found that the use of silicon carbide as an absorbing filler in the composite is very promising, providing a high temperature of its heating at dissipation of microwave energy. At the same time, the results of in-situ experiment of measuring dielectric properties of composites with different fillers and numerical results showed convergence with an error of 14%. The obtained results can be used in the creation of new radio-absorbing composites on the polymer basis with a given complex of functional properties.

We demonstrate that CPT-violation due to e+e− mass difference generates a non-zero photon mass. As a result the cosmological bounds on the photon mass lead to the bounds on e+e− mass difference which are at least by 10 orders of magnitude stronger than the direct experimental bound.

Photon mass and Heaviside force

Pulsars are magnetized rotating compact objects. They spin down due to magnetic dipole radiation and wind emission. If a photon has nonzero mass, the spin-down rate will be lower than in the zero-mass case. We show that an upper limit of the photon mass, i.e., , may be placed if a pulsar with period P is observed to spin down. Recently, a white dwarf (WD)–M dwarf binary, AR Scorpii, was discovered to emit pulsed broadband emission. The spin-down luminosity of the WD can comfortably power non-thermal radiation from the system. Applying our results to the WD pulsar with P = 117 s, we obtain a stringent upper limit of the photon mass between , assuming a vacuum dipole spindown, and , assuming spindown due to a fully developed pulsar wind.

In this paper we give a kind of representation formula for a null curve with null arclength parameter in three dimensional Minkowski spacetimeE31and define structure function ofsuch null curve. Using this representation formula and relations between the null curvature functionand structure function of null curve, especially by solving certain differential equations, we obtainsome characterizations and classifications of some special null curves.

Gauge-invariant descriptions for a free bosonic scalar field of continuous spin in a [Formula: see text]-dimensional Minkowski space–time using a metric-like formulation are constructed on the basis of a constrained BRST–BFV approach we propose. The resulting BRST–BFV equations of motion for a scalar field augmented by ghost operators contain different sets of auxiliary fields, depending on the manner of a partial gauge-fixing and a resolution of some of the equations of motion for a BRST-unfolded first-stage reducible gauge theory. To achieve an equivalence of the resulting BRST-unfolded constrained equations of motion with the initial irreducible Poincaré group conditions of a Bargmann–Wigner type, it is demonstrated that one should replace the field in these conditions by a class of gauge-equivalent configurations. Triplet-like, doublet-like constrained descriptions, as well as an unconstrained quartet-like non-Lagrangian and Lagrangian formulations, are derived using both Fronsdal-like and new tensor fields. In particular, the BRST–BV equations of motion and Lagrangian using an appropriate set of Lagrangian multipliers in the minimal sector of the respective field and antifield configurations are constructed in a manifest way.

Maxwell equations are studied for a vacuum with nonzero conductivity coefficient. The loss of energy of a photon during its propagation through this vacuum is calculated and the nonzero rest mass of the photon is shown to be related to the conductivity coefficient of the vacuum. The dissipative mechanism is investigated considering a conformally fluctuating metric in the Einstein equation. Possible astrophysical consequences are discussed.

We investigate the charged-neutral difference in the pion self-energy at finite temperature T. Within chiral perturbation theory (ChPT) we extend a previous analysis performed in the chiral and soft pion limits. Our analysis with physical pion masses leads to additional non-negligible contributions for temperatures typical of a meson gas, including a momentum-dependent function for the self-energy. In addition, a nonzero imaginary part arises to leading order, which we define consistently in the Coulomb gauge and comes from an infrared enhanced contribution due to thermal bath photons. For distributions typical of a heavy-ion meson gas, the charged and neutral pion masses and their difference depend on temperature through slowly increasing functions. Chiral symmetry restoration turns out to be ultimately responsible for keeping the charged-neutral mass difference smooth and compatible with the observed charged and neutral pion spectra. We study also phenomenological effects related to the thermal electromagnetic damping, which gives rise to corrections for transport coefficients and distinguishes between neutral and charged mean free times. An important part of the analysis is the connection with chiral symmetry restoration through the relation of the pion mass difference with the vector-axial spectral function difference, which holds at T ¼ 0 due to a sum rule in the chiral and soft pion limits. We analyze the modifications of that sum rule including nonzero pion masses and temperature, up to OðT2Þ ∼ OðM2 πÞ. Both effects produce terms making the pion mass difference grow against chiral-restoring decreasing contributions. Finally, we analyze the corrections to the previous ChPT and sum rule results within the resonance saturation framework at finite temperature, including explicitly ρ and a1 exchanges. Our results show that the ChPT result is robust at low and intermediate temperatures, the leading resonance corrections within this framework being OðT2M2 π=M2 RÞ with MR the involved resonance masses.

We consider the finite temperature Casimir effect between two concentric spheres due to the vacuum fluctuations of the electromagnetic field in the ($D+1$)-dimensional Minkowski spacetime. Different combinations of perfectly conducting and infinitely permeable boundary conditions are imposed on the spheres. The asymptotic expansions of the Casimir free energies when the dimensionless parameter $\ensuremath{\epsilon}$, the ratio of the distance between the spheres to the radius of the smaller sphere, is small are derived in both the high temperature region and the low temperature region. It is shown that the leading terms agree with those obtained using the proximity force approximation, which are of order $T{\ensuremath{\epsilon}}^{1\ensuremath{-}D}$ in the high temperature region and of order ${\ensuremath{\epsilon}}^{\ensuremath{-}D}$ in the low temperature region. Some universal structures are observed in the next two correction terms. The leading terms of the thermal corrections in the low temperature region are also derived. They are found to be finite when $\ensuremath{\epsilon}\ensuremath{\rightarrow}{0}^{+}$ and are of order ${T}^{D+1}$.