How Stable is the Photon?

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.

Electromagnetic memory effect is the residual velocity (a kick) acquired by free charges following the passage of electromagnetic waves. We compute the electromagnetic memory effect in de Broglie-Proca theory for particle scattering in four dimensional Minkowski spacetime as a function of the photon mass, and show that it is suppressed by Yukawa decay compared to usual Maxwell electrodynamics. Therefore, we suggest that its experimental detection would place bounds on, or potentially exclude, the existence of non-zero photon mass.

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 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

An additional U(1) symmetry predicted in theories beyond the Standard Model of particle physics can give rise to hidden (dark) photons. Depending on the mass and density of these hidden photons, they could account for a large fraction of the Dark Matter observed in the Universe. When passing through an interface of materials with different dielectric properties, hidden photons are expected to produce a tiny flux of photons. The wavelength of these photons is directly related to the mass of the hidden photons. In this contribution we report on measurements covering the visible and near-UV spectrum, corresponding to a dark photon mass in the eV range. The data were taken with the FUNK experiment using a spherical mirror of $\sim$14m$^{2}$ total area built up of 36 aluminum segments.

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.

The 12th international symposium, The Vigier Centenary - 3rd Regime Natural Science Towards a Physics of The Observer: Honoring Noted Mathematical Physicist Jean-Pierre Vigier, 20-23 September 2021, was postponed three times due to travel restrictions imposed by the Coronavirus pandemic. The conference was originally to be held in historic Liege, Belgium, but ended up with a Virtual Meeting venue at the Noetic Advanced Studies Institute, Escalante Desert Research Facility, Beryl, Utah, USA. This symposium – the Centenary of J-P Vigier’s birth (January 16, 1920 Paris, France to May 4, 2004, Paris, France) marks the final conference in the series running for 27-years.Vigier was often called ‘Le Heretique du Physique’ in the French media. Most of his work – over 400 papers, chapters and books relates to cutting-edge extensions or alternative interpretations to ‘mainstream physics’ such as photon mass, or the de Broglie-Bohm-Vigier Causal-Stochastic Interpretation of Quantum Mechanics for example.Einstein asked Vigier to become his assistant at Princeton’s Advanced Studies Institute; but since Vigier was ‘politically involved’ with the French in Vietnam the US government would not allow him entry to the USA at that time. Thus, he became Nobelist Louis de Broglie’s assistant instead.The Vigier conference began in 1995, with the first two conferences held at York University in Toronto, Canada. It was one of a handful of such Avant-garde series ‘allowing’ physicists to color outside-the-box; including CASYS, PIRT and ANPA, which emerged in the last decades of the 20th-century to cover areas of fundamental physics which at that time had no obvious outlet for discussion. These are vital areas for discussion now, but at the time, particle physics was thought solved by string theory and supersymmetry, and gravity by various approaches to quantizing general relativity.A surprise is likely to occur with the looming experimental awakening of the imminent paradigm shift to 3rd regime Natural Science; current thinking, for all practical purposes, insists that gravity must be quantized. This arises from the belief that the quantum mechanical stochastic foam is an impenetrable basement of reality. String theory (now a 12D M-theory), an evolution of 5D Kaluza-Klein theory, has been developed as the putative theory of quantum gravity; but there is no a priori reason that gravity must be quantized. The Standard Model (SM) of particle physics and cosmology, while known to be incomplete, still myopically governs ‘allowed’ research avenues.

Extensions of the standard model of particle physics, in particular those based on string theory, often predict a new U(1) gauge symmetry in a hidden sector. The corresponding gauge boson, called hidden photon, naturally interacts with the ordinary photon via gauge kinetic mixing, leading to photon - hidden photon oscillations. In this framework, one expects photon disappearance as a function of the mass of the hidden photon and the mixing angle, loosely constrained from theory. Several experiments have been carried out or are planned to constrain the mass-mixing plane. In this contribution we derive new constraints on the hidden photon parameters, using very high energy gamma-rays detected from the Crab Nebula, whose broad-band spectral characteristics are well understood. The very high energy gamma-ray observations offer the possibility to provide bounds in a broad mass range at a previously unexplored energy and distance scale. Using existing data that were taken with several Cherenkov telescopes, we discuss our results in the context of current constraints and consider the possibilities of using astrophysical data to search for hidden photon signatures.

The rapid increase of traffic in intra-data center (DC) networks has motivated nanosecond-scale wavelength switching laser, such as fast wavelength switchable laser [1], [2] and semiconductor optical amplifier (SOA) switched based wavelength arrays [3], to overcome DC networks' scalability bottlenecks in radix and bandwidth [2], [3]. Besides switching time, the demand on high-capacity triggers research into optically switched coherent communications that require light sources to be simultaneously low linewidth and fast switchable. These two requirements, however, are inherently contradictory as narrow linewidth requires a long photon lifetime (thus low switching speed), while fast switching requires a short photon lifetime and high modulation BW. In this work, we investigate linewidth and switching speed behaviour of a fast switchable laser under optical injection locking (OIL) technique [4]. Although OIL for linewidth improvement has been investigated in many previous works, it has not been demonstrated for fast switching lasers. Our contribution here focuses on experimental study of the dynamic behaviour of fast switching laser under OIL, specifically the frequency variation and phase noise during switching and stable operation periods, as well as the impact of OIL power.

Many extensions to the Standard Model (SM) introduce a hidden or dark sector (DS) to provide candidates for dark matter in the universe and an explanation to astrophysical observations such as the positron excess observed in the cosmic radiation flux. This hidden sector could rise from an additional U(1)d gauge symmetry. ATLAS has searched for the gauge boson of the DS, which could be a massless or massive dark photon that either kinetically mixes with the SM photon or couples to the Higgs sector via some mediators. If dark photons decay in turn to SM particles with a significant branching ratio, we could either observe measurable deviations in some particular Higgs boson decay channels or new exotic signatures that would be accessible at the Large Hadron Collider (LHC) energies.

In this paper, we extend Rothemund and Winfree's examination of the tile complexity of tile self-assembly [6]. They provided a lower bound of Ω(log N/log log N) on the tile complexity of assembling an N × N square for almost all N. Adleman et al. [1] gave a construction which achieves this bound. We consider whether the tile complexity for self-assembly can be reduced through several natural generalizations of the model. One of our results is a tile set of size O(√log N) which assembles an N × N square in a model which allows flexible glue strength between non-equal glues (This was independently discovered in [3]). This result is matched by a lower bound dictated by Kolmogorov complexity. For three other generalizations, we show that the Ω(log N/log log N) lower bound applies to N × N squares. At the same time, we demonstrate that there are some other shapes for which these generalizations allow reduced tile sets. Specifically, for thin rectangles with length N and width k, we provide a tighter lower bound of Ω(N(1/k)/k) for the standard model, yet we also give a construction which achieves O(log N/log log N) complexity in a model in which the temperature of the tile system is adjusted during assembly. We also investigate the problem of verifying whether a given tile system uniquely assembles into a given shape, and show that this problem is NP-hard.

We propose an extension of the Standard Model (SM) with a ${U}_{{A}^{\ensuremath{'}}}(1)$ gauge-invariant dark sector connected to the SM via a new portal---the Stueckelberg portal, arising in the framework of dark photon ${A}^{\ensuremath{'}}$ mass generation via the Stueckelberg mechanism. This portal opens through the effective $\mathrm{dim}=5$ operators constructed from the covariant term of the auxiliary Stueckelberg scalar field $\ensuremath{\sigma}$ providing flavor nondiagonal renormalizable couplings of both $\ensuremath{\sigma}$ and ${A}^{\ensuremath{'}}$ to the SM fermions $\ensuremath{\psi}$. The Stueckelberg scalar plays a role of Goldstone boson in the generation of mass of the dark photon. Contrary to the conventional kinetic mixing portal, in our scenario, flavor diagonal ${A}^{\ensuremath{'}}\ensuremath{-}\ensuremath{\psi}$ couplings are not proportional to the fermion charges and are, in general, flavor nondiagonal. These features drastically change the phenomenology of dark photon ${A}^{\ensuremath{'}}$ relaxing or avoiding some previously established experimental constraints. We focus on the phenomenology of the described scenario of the Stueckelberg portal in the lepton sector and analyze the contribution of the dark sector fields ${A}^{\ensuremath{'}}$ to the anomalous magnetic moment of muon $(g\ensuremath{-}2{)}_{\ensuremath{\mu}}$, lepton flavor--violating decays ${l}_{i}\ensuremath{\rightarrow}{l}_{k}\ensuremath{\gamma}$, and $\ensuremath{\mu}\ensuremath{-}e$ conversion in nuclei. We obtain limits on the model parameters from the existing data on the corresponding observables.

Gravitational production of massive particles due to cosmic expansion can be significant during the inflationary and reheating period of the Universe. If the particle also has non-gravitational interactions that do not significantly affect its production, numerous observational probes open up, including cosmological probes. In this work, we focus on the gravitational production of light vector bosons that couple feebly to the Standard Model (SM) particles. Due to the very feeble coupling, the light vector bosons never reach thermal equilibrium, and if the Hubble scale at the end of inflation is above 108 GeV, the gravitational production can overwhelm the thermal production via the freeze-in mechanism by many orders of magnitude. As a result, much stronger constraints from the Big Bang Nucleosynthesis (BBN) can be placed on the lifetime and mass of the vector bosons compared to the scenario where only thermal production is considered. As an example, we study the sub-GeV scale dark photons, which couple to the SM only through kinetic mixing, and derive constraints on the mass and kinetic mixing parameter of the dark photon from the photodisintegration effects on the light element abundances relevant at the end of the BBN when the cosmic age was around 104 s.