Light In Vacuum Research Articles

Light speed variation from GRB 221009A

It is postulated in Einstein’s relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed, and a series of studies on high-energy photon events from gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) suggest a light speed variation with E LV = 3.6 × 1017 GeV or a bound E LV ≥ 3.6 × 1017 GeV. From the newly observed gamma-ray burst GRB 221009A, we find that a 99.3 GeV photon detected by Fermi-Large Area Telescope (LAT) is coincident with the sharp spike in the light curves detected by both Fermi-Gamma-ray Burst Monitor (GBM) and HEBS under the above scenario of light speed variation, suggesting an option that this high-energy photon was emitted at the same time as a sharp spike of low-energy photon emission at the GRB source. Thus this highest energy photon event detected by Fermi-LAT during the prompt emission of GRBs might be considered as an optional signal for the linear form modification of light speed in cosmological space.

Cosmic time calibrator for wireless sensor network

Time synchronization of sensor nodes is critical for optimal operation of wireless sensor networks (WSNs). Since clocks incorporated into each node tend to drift, recurrent corrections are required. Most of these correction schemes involve clients periodically receive RF timing signals from a time server. However, an RF-based scheme is prone to glitches or failure unless operating in a region with almost entirely unobstructed space; hence it only operates well in a limited range of environments. For example, GPS requires open-sky environments. Moreover, the precision of land-based RF schemes is limited to a few micro seconds. In this work, we report on a more versatile and new type of recurrent clock resynchronization scheme called cosmic time calibrator (CTC) and its development and testing. CTC utilizes cosmic-ray muon signals instead of RF signals. Muons are penetrative and continuously precipitating onto the Earth’s surface, and they tend to travel linearly through encountered matter at approximately the speed of light in vacuum. Therefore, muons themselves can periodically transfer the precise timing information from node to node; hence, the performance of the inter-nodal communication device such as Wi-Fi or Bluetooth is minimized/unnecessary for an online/offline WSN analysis. The experimental results have indicated that a resynchronization frequency and precision of 60 Hz and ± 4.3 ns (S.D.) can be achieved. Modelling work of the WSN-based structural health monitoring of aerospace structures has shown that CTC can contribute to the development of new critical and useful applications of WSN in a wider range of environments.

Time is suspect!

‘That it is possible to find the form of the Lorentz transformations without requiring the speed of light to be the same in every inertial system is rediscovered about every thirty years and, rightly, forgotten.’ This proposition alongside the doctoral dissertation of Hendrik Smid in 1986 provides food for thought: Is the light postulate of special relativity, which gives the speed of light in vacuum its status of maximum and unchanging speed, indeed not necessary? What kind of physical world are you then left with? What could be the value of discussing this in class? In this paper we show how the Lorentz transformation, which describes the relationship between two coordinate systems moving relative to each other at a constant speed, can indeed be derived by replacing the light postulate by another assumption, namely the requirement of closure under composition of transformations that relate inertial frames of reference (i.e. two successive coordinate transformations of certain type can be written as one transformation of the same type). Although well known in specialised literature of physics research, the remarkable insight that is somehow buried in nature is hardly mentioned in pre-university and bachelor’s physics courses and textbooks. Yet, the presented comprehensible approach may support the understanding and plausibility of the abstract subject of special relativity. Mathematics may go too far for an average pre-university student, but this subject would certainly not be out of place in an undergraduate physics course or a physics teacher course. Although many teachers do not know that the light postulate of special relativity can be replaced by another assumption or may not appreciate such replacement as part of their teaching of the topic, it offers in our opinion an opportunity to inform students that a critical look at postulates and an investigation of alternatives is an essential part of the nature of science.

Gap solitons on an integrated CMOS chip

Abstract Nonlinear propagation in periodic media has been studied for decades, yielding demonstrations of numerous phenomena including strong temporal compression and slow light generation. Gap solitons, that propagate at frequencies inside the stopband, have been observed in optical fibres but have been elusive in photonic chips. In this manuscript, we investigate nonlinear pulse propagation in a chip-based nonlinear Bragg grating at frequencies inside the stopband and observe clear, unequivocal signatures of gap soliton propagation, including slow light, intensity-dependent transmission, intensity-dependent temporal delay and gap soliton compression. Our experiments which are performed in an on-chip ultra-silicon-rich nitride (USRN) Bragg grating with picosecond time scales, reveal slow light group velocity reduction to 35%–40% of the speed of light in vacuum, change in the temporal delay of 7 ps at low peak powers between 15.7 W–36.6 W, which is accompanied by up to 2.7× temporal compression of input pulses. Theoretical calculations using the nonlinear coupled mode equations confirm the observations of intensity-dependent temporal delay. Of fundamental importance, this demonstration opens up on-chip platforms for novel experimental studies of gap solitons as the basis of all-optical buffers, delay lines and optical storage.

Fundamental Physical Constants and Primary Physical Parameters

Every four years the Committee on Data for Science and Technology (CODATA) supplies a self-consistent set of values of the basic constants and conversion factors of physics recommended for international use. In 2013, the World-Universe Model (WUM) proposed a principally different depiction of the World as an alternative to the picture of the Big Bang Model. This article: 1) Gives the short history of Classical Physics before Special Relativity; 2) Calculates Fundamental Physical Constants based on experimentally measured Rydberg constant, Electrodynamic constant, Electron Charge-to-Mass Ratio, and Planck constant; 3) Discusses Electrodynamic constant and Speed of Light; 4) Considers Dimensionless Fundamental Parameters (Dirac Large Number Q and Dimensionless Rydberg Constant α); 5) Calculates Newtonian Constant of Gravitation based on the Inter-connectivity of Primary Physical Parameters; 6) Makes a detailed analysis of the Self-consistency of Fundamental Physical Constants and Primary Physical Parameters through the prism of WUM. The performed analysis suggests: 1) Discontinuing using the notion “Vacuum” and its characteristics (Speed of Light in Vacuum, Characteristic Impedance of Vacuum, Vacuum Magnetic Permeability, Vacuum Electric Permittivity); 2) Accepting the exact numerical values of Electrodynamic constant, Planck constant, Elementary charge, and Dimensionless Rydberg Constant α. WUM recommends the predicted value of Newtonian Constant of Gravitation in 2018 to be considered in CODATA Recommend Values of the Fundamental Physical Constants 2022.

Research and Simulation of Negative Group Delay and Superluminal Propagation

Abstract In recent years, negative group delay circuits have attracted much attention due to their propagation characteristics and wide application prospects. In the history of human exploration, the exploration of the speed of light has never stopped. The theory of relativity points out that the speed of light in vacuum is the limit speed of signal propagation. However, it is found through research that phase velocity and group velocity appear faster than the speed of light, which does not violate the causal relationship. This paper first introduces the related concepts of negative group delay and superluminal phenomenon, the second focuses on the principle of negative group delay and superluminal phenomenon in-depth analysis and research, finally using the principle of Multisim software, the bandwidth of two different job, different structure of circuit design, the virtual simulation experiment to negative group delay phenomenon and measurement data. It is of great significance to explore the field of faster-than-light and negative group delay in today's rapidly developing information age, and it can try to meet the high requirements for signal transmission. In the future, the interdisciplinary research direction of this research topic also has great development space.

Variable Physical Constants and Beyond

We previously revealed that the speed of light in vacuum c, the gravitational constant G, the vacuum permittivity ε, and the vacuum permeability μ can be defined by the temperature T (or the expected average frequency f) of cosmic microwave background (CMB) radiation. Given that CMB is continuously cooling, that is, T is continuously decreasing, we proposed that the above “constants” are variable and their values at some space-time with CMB temperature T (cT, GT, εT, and μT) can be described using their values (c0, G0, ε0, and μ0) and the temperature (T0) of CMB at present space-time. Based on the above observation, a number of physical equations related with these constants are re-described in this study, including relativity equation, mass-energy equation, and Maxwell’s equations, etc.

Using the average air temperature along the trace for atmospheric correction in laser ranging: accuracy analysis

One of the factors affecting the results of laser ranging measurements on ground-level traces is the difference between the speed of light propagation in the Earth’s atmosphere and the speed of light in vacuum. This difference is accounted for by the introduction of a correction for the mean integral refractive index of air along the measured trace. Research to improve the accuracy of such a correction is one of the most important scientific fields in geodesy and metrology. At the same time, the empirical approach to accounting for the atmospheric influence, which does not have a strict justification, is used in geodetic practice and involves determining the mean integral refractive index by the average air temperature along the measured trace. The paper is dedicated to the analysis of the accuracy of this empirical approach and to the estimation of the possibility of its application for providing traceability in the practice of linear measurements.

Measurement of single nanoparticle anisotropy by laser induced optical alignment and Rayleigh scattering for determining particle morphology

We demonstrate the measurement of nanoparticle anisotropy by angularly resolved Rayleigh scattering of single optical levitated particles that are oriented in space via the trapping light in vacuum. This technique is applied to a range of particle geometries from perfect spherical nanodroplets to octahedral nanocrystals. We show that this method can resolve shape differences down to a few nanometers and be applied in both low-damping environments, as demonstrated here, and in traditional overdamped fluids used in optical tweezers.

The Number of Elementary Fermions and the Electromagnetic Coupling

Electric charges and masses of elementary fermions of the Standard Model and fundamental physical constants (speed of light in vacuum, Planck constant, gravitational constant, vacuum permittivity, electron charge) are related through a simple equation. This new relation links 10 of the free parameters of the Standard Model—the masses of the three charged leptons and six quarks, and the electromagnetic coupling—in a compact formula, leaving strong constraints for allowing further elementary charged fermions beyond the Standard Model’s physics. The formula is not derived by theoretical calculations, but it is based on the empirically measured values of the electric charges and proper masses of the known elementary fermions.

IRREGULARITIES IN THE USE OF THE MODERN SPANISH LANGUAGE

The language errors could potentially hinder the transmission of information and disturb theconcretization of the act of communication. In the contemporary context, many factors exercise influence on thelanguage especially the social media triggering disregard of the linguistic norms, devaluing the correct use of thelanguage and disrupting the normal flow of communication. These irregularities in the use of the Spanish languageare known as language vices. The subject of this paper is a broad view of the irregularities (that could be of differentgrammatical nature) that could result from the improper use of the Modern Spanish language and encompasses thedefinition, review of the most common types of language vices (pleonasm, solecism, amphibology, barbarism,archaism, and neologism) supported by a series of examples excerpted from relevant sources among whichOrtografía de la lengua Española (RAE:2010). Diccionario panhispánico de dudas (RAE:2005), Gran diccionariode sinónimos, voces afines e incorrecciones (Fernando Corripio, Bruguera, 1979), etc. The purpose of the paper is,in absence of Spanish grammar(s) in Macedonian language and published comparative papers in particular in thefield of lexicology, to fill to some extant the vacuum and shed light on the language vices in the Modern Spanishlanguage, thus arousing the interest of the Macedonian linguists, especially those with knowledge of Spanish forfuture more profound research and their systematization.

Excitation of semiconductor nanosystems by a few-photon frequency-multimode optical field

The excitation of a semiconductor quantum nanosystem induced by a frequency-multimode nonclassical electromagnetic field is analytically investigated. The possibility to control the features and dynamics of different excitation channels by varying the weights and initial energy distribution in the considered field spectral modes is demonstrated. Strong coupling between different frequency modes is found to arise due to their interaction with electronic subsystem and is shown to influence dramatically on the excitation. The peculiarities of the excitation process induced by a multi-frequency Schmidt mode, which characterizes spectral distribution of squeezed vacuum light, are revealed. The optimal spectral profile of the Schmidt mode and initial energy distribution of different field spectral components providing the most efficient excitation of a nanosystem are found.

Sensitivity enhancement of a dispersive cavity with squeezed vacuum light injection

The measurement sensitivity of a cavity could be enhanced for sensing applications in an anomalous dispersion condition. In this paper, we find that when injecting a squeezed vacuum light into a dispersive cavity, the sensitivity could be improved further, even beating the standard quantum limit at the detuning frequencies via controlling the dispersion condition. It is amazing that normal dispersion is superior to anomalous dispersion in improving the measurement sensitivity in the presence of a squeezed vacuum field. It implies this paper could be used to realize high-precision sensing applications.

Inflation with Einstein-Gauss-Bonnet, non-minimal, and non-minimal derivative couplings: the constant-roll condition

In our research, we consider and study the inflation theories of Einstein-Gauss-Bonnet, minimal, non-minimal, and non-minimal derivative coupling with the constant-roll condition. Given the gravitational wave event, GW170817, which produces the speed of gravitational waves that was almost equal to the speed of light in vacuum, we constrain that the speed of the tensor perturbation was nearly equal to unity, . We involve a scalar field potential whose function can be obtained from an equation of motion by choosing the Gauss-Bonnet coupling functions. We use the linear and quadratic coupling functions, which are their simplest functions. The one result obtained are able to produce observed quantities such as the spectral index for scalar perturbation, ns = 0.9642, the spectral index for tensor perturbation, nT = −5.2471 × 10−4, and tensor-scalar ratio, r = 0.0041, which are compatible with the newest Planck data using the slow-roll parameters obtained analytically.

Speeds of Wave Propagation in Ideal Gaseous Molecular and Neutrino Media.

The neutrino mass values extracted from the pioneering Nobel Prize winning measurements of Kajita and co-workers at Superkamiokande were used in the classical Newton-Laplace equation for computing the speed of propagation of acoustic waves in gases comprising neutrinos. It is found that, surprisingly, acoustic waves in the lightest neutrino environments proceed with the speed of light in vacuum, c. This allows for the computation of c in terms of the lightest neutrino mass within 1% and is consistent with the fact that gravitational waves have been recently found to propagate with the speed of light. It is also found that the rest energy, m1c2, of the lightest neutrinos coincides with the photon energy at the cosmic background radiation temperature (CMBR). These findings are discussed in terms of the dual nature of photons and its possible interrelation with the omnipresent neutrinos. The present results also confirm that neutrino gases behave as ideal gases with only one-half of a translational degree of freedom, consistent with their one-dimensional, and practically one-directional, degree of freedom.

Fundamental issues with light propagation through PT -symmetric systems

We analyze the emergence of unphysical superluminal group velocities in Su-Schrieffer-Heeger (SSH) parity-time ($\mathcal{PT}$) symmetric chains, and explore the origins of such a behavior. By comparing the band structure of an infinite loss-gain SSH chain with that of a continuous realization---a one-dimensional Bragg stack governed by the Helmholtz equation---we first exclude insufficient coupling consideration in the tight-binding description as the cause of group-velocity divergence. We then focus on material dispersion, and show that indeed, restoring causality in the description of both the lossy and the gain components resolves the problem and recovers finite group velocities, whose real part can only exceed the speed of light in vacuum when accompanied by a significant imaginary part. Our analysis introduces thus the required practical limits in the performance of common $\mathcal{PT}$-symmetric systems.

Relativity, scaling, and electromagnetic radiation equilibrium for circular orbits

The radiation emitted by a charged particle moving in a circular orbit requires that the orbital speed of the particle is less than the speed of light in vacuum. This crucial relativistic restriction is lost in any treatment which combines nonrelativistic mechanics with classical electrodynamics through the nonrelativistic Larmor radiation formula or the dipole approximation, which approximations correspond to taking only the lowest power of velocity. A notable example of the resulting failure involves the derivation of the blackbody radiation spectrum within classical physics. Nature contains a smallest electric charge e and a largest speed c. Both these fundamental constants should appear in a classical theory of nature. We connect the assumptions regarding fundamental constants to the scaling aspects of classical theories. Nonrelativistic mechanics exhibits scaling which is entirely different from that found in relativistic classical electrodynamics where only Coulomb potentials are allowed and the constants e and c both appear. The scaling aspects are reflected in the radiation spectra which different theories predict for thermal radiation equilibrium. The Rayleigh–Jeans spectrum reflects the scaling aspects of nonrelativistic classical mechanics whereas the classical electromagnetic zero-point spectrum and the Planck spectrum share the scaling aspects of relativistic classical electrodynamics which includes both e and c.

Synthesis of near-diffraction-free orbital-angular-momentum space-time wave packets having a controllable group velocity using a frequency comb.

Novel forms of light beams carrying orbital angular momentum (OAM) have recently gained interest, especially due to some of their intriguing propagation features. Here, we experimentally demonstrate the generation of near-diffraction-free two-dimensional (2D) space-time (ST) OAM wave packets (ℓ = +1, +2, or +3) with variable group velocities in free space by coherently combining multiple frequency comb lines, each carrying a unique Bessel mode. Introducing a controllable specific correlation between temporal frequencies and spatial frequencies of these Bessel modes, we experimentally generate and detect near-diffraction-free OAM wave packets with high mode purities (>86%). Moreover, the group velocity can be controlled from 0.9933c to 1.0069c (c is the speed of light in vacuum). These ST OAM wave packets might find applications in imaging, nonlinear optics, and optical communications. In addition, our approach might also provide some insights for generating other interesting ST beams.

Determination of weakly squeezed vacuum states through photon statistics measurement

Weakly squeezed vacuum light, especially when resonant with an atomic transition, plays an important role in quantum storage and the generation of various quantum sources. However, achieving a weak squeezing measurement with a precision better than 0.01 dB by means of typical homodyne detection (HD) is still very challenging due to the low signal-to-noise ratio and the limited resolution of HD systems. Here, we provide an alternative method based on photon statistics measurement to determine the weak squeezing of the squeezed vacuum light generated from an optical parametric oscillator (OPO) working far below the threshold, and we establish the relationship between the squeezing parameter and the second-order degree of coherence. The experimental results agree well with the theoretical analysis. The advantages of this method are that it provides a feasible and reliable experimental measure to determine weak squeezing with high precision and that the measurement is independent of the detection efficiency. This method can be used to measure other quantum features for various quantum states with extremely weak nonclassicality.

Speed of sound in dense matter and two families of compact stars

The existence of massive compact stars (M ≳ 2.1 M⊙) implies that the speed of sound exceeds the conformal limit (cs2 = 1/3 × the squared speed of light in vacuum) if those stars have an inner and outer crust of ordinary nuclear matter. Here, we show that if the most massive objects are strange quark stars, namely, stars entirely composed of quarks, cs can assume values below the conformal limit even while observational limits on those objects are also satisfied. By using astrophysical data associated with those massive stars derived from electromagnetic and gravitational wave signals, we use a Bayesian analysis framework and by adopting a constant speed of sound equation of state to show that the posterior distribution of cs2 is peaked around 0.3 and the maximum mass of the most probable equation of state is ∼2.13 M⊙. We discuss which new data would require a speed of sound larger than the conformal limit even when considering strange quark stars. In particular, we analyze the possibility that the maximum mass of compact stars is larger than 2.5 M⊙, as it would be if the secondary component of GW190814 would turn out to be a compact star – and not a black hole, as previously assumed. Finally, we discuss how the new data for PSR J0740+6620 obtained by the NICER collaboration compare with our results and find they are in qualitative agreement. We conclude with a brief discussion of other possible interpretations of our analysis.