Physical Nature Research Articles

Random Holography: Generating EPR‐Like Correlation with Thermal Photons

AbstractEntanglement and correlation of photons play a central role in quantum information and communication. There are two types of photon correlations: one usually exists in a two‐particle entangled state first conceived by Einstein, Podolsky, and Rosen (EPR) in 1935, while the other occurs in a thermal light source found by Hanbury Brown and Twiss (HBT) in 1956. Many studies are concerned with the physical nature and differences behind the two types of photon correlations. Here, a holography‐inspired linear optical system that generates a pair of conjugate chaotic beams is proposed, which include both HBT‐type and EPR‐like correlations. From principle to experimental generation, the study presents a classical paradigm of a simple bi‐correlation light source for diverse quantum‐mimic applications such as two‐photon imaging.

Quasi-Classical Models of Nonlinear Relaxation Polarization and Conductivity in Electric, Optoelectric, and Fiber Optic Elements Based on Materials with Ionic–Molecular Chemical Bonds

A generalized scientific review with elements of additions and clarifications has been carried out on the methods of theoretical research on the electrophysical properties of crystals with ionic–molecular chemical bonds (CIMBs). The main theoretical tools adopted are the methods of quasi-classical kinetic theory as applied to ionic subsystems relaxing in layered dielectrics (natural silicates, crystal hydrates, various types of ceramics, and perovskites) in an electric field. A universal (applicable for any CIMBs class crystals) nonlinear quasi-classical kinetic equation of theoretical and practical importance has been constructed. This equation describes, in complex with the Poisson equation, the mechanism of ion-relaxation polarization and conductivity in a wide range of polarizing field parameters (0.1–1000 MV/m) and temperatures (1–1550 K). The physical model is based on a system of non-interacting ions (due to the low concentration in the crystal) moving in a one-dimensional, spatially periodic crystalline potential field, perturbed by an external electric field. The energy spectrum of ions is assumed to be continuous. Elements of quantum mechanical theory in a quasi-classical model are used to mathematically describe the influence of tunnel transitions of hydrogen ions (protons) during the interaction of proton and anion subsystems in hydrogen-bonded crystals (HBC) on the polarization of the dielectric in the region of nitrogen (50–100 K) and helium (1–10 K) temperatures. The mathematical model is based on the solution of a system of nonlinear Fokker-Planck and Poisson equations, solved by perturbation theory methods (via expanding solutions into infinite power series in a small dimensionless parameter). Theoretical frequency and temperature spectra of the dielectric loss tangent were constructed and analyzed, the molecular parameters of relaxers were calculated, and the physical nature of the maxima of the experimental temperature spectra of dielectric losses for a number of HBC crystals was discovered. The low-temperature maximum, which is caused by the quantum tunneling of protons and is absent in the experimental spectra, was theoretically calculated and investigated. The most effective areas of scientific and technical application of the theoretical results obtained were identified. The application of the equations and recurrent formulas of the constructed model to the study of nonlinear optical effects in elements of laser technologies and nonlinear radio wave effects in elements of microwave signal control systems is of the greatest interest.

Influence of the nature of the distribution of recombination centers in the space charge region of the p–n junction on the parameters of the current–voltage characteristics within the classical Shockley and Shockley–Noyce–Sah models

Abstract The behavior of current–voltage characteristics (CVC) within the classical Shockley and Shockley–Noyce–Sah models depending on the nature of the distribution of recombination centers in the space charge region of the p–n junction was analyzed. Notably, the non-ideality factor determined from experimental CVC cannot be introduced into the exponent of the mathematical model of the CVC because it is unrelated to the physical nature of the exponentials of classical models but indicates the voltage dependence of the pre-exponential factor of the recombination component of the total current. The exponential factor of the model with a non-ideality factor describing the experimental CVC presents only a mathematical approximation of a small portion of it.

Micro-Transfer printing of InGaAs/InP Avalanche Photodiode on Si Substrate

Abstract We report on the fabrication and micro-transfer printing of InGaAs/InP avalanche photodiodes (APDs) onto silicon substrates. A process flow was developed to suspend the devices using semiconductor tethers. The developed process reduces the number of fabrication steps required compared to methods based on the use of photoresist tethers. Furthermore, our process is compatible with devices that may be susceptible to damage induced by the photoresist removal process. APDs were characterised in linear mode operation both before suspension and after printing. Despite the additional fabrication steps required to suspend the APD membranes and the physical nature of the micro-transfer printing process, the electrical characteristics of the devices were preserved. No degradation in the optical performance of the devices was measured. Our work represents the first demonstration of micro-transfer printing of InGaAs/InP avalanche photodiodes onto silicon substrates. The results highlight the viability of micro-transfer printing for effective heterogeneous integration of InGaAs/InP avalanche photodiodes with silicon photonic integrated circuits for optical and quantum communication and other light detection applications.

Quantum null geometry and gravity

In this work, we demonstrate that quantizing gravity on a null hypersurface leads to the emergence of a CFT associated with each null ray. This result stems from the ultralocal nature of null physics and is derived through a canonical analysis of the Raychaudhuri equation, interpreted as a constraint generating null time reparametrizations. The CFT exhibits a non-zero central charge, providing a mechanism for the quantum emergence of time in gravitational systems and an associated choice of vacuum state. Our analysis reveals that the central charge quantifies the degrees of freedom along each null ray. Throughout our investigation, the area element of a cut plays a crucial role, necessitating its treatment as a quantum operator due to its dynamic nature in phase space or because of quantum backreaction. Furthermore, we show that the total central charge diverges in a perturbative analysis due to the infinite number of null generators. This divergence is resolved if there is a discrete spectrum for the area form operator. We introduce the concept of ‘embadons’ to denote these localized geometric units of area, the fundamental building blocks of geometry at a mesoscopic quantum gravity scale.

Security Challenges, Mitigation Strategies, and Future Trends in Wireless Sensor Networks: A Review

Wireless Sensor Networks (WSNs) represent an innovative technology that integrates compact, energy-efficient sensors with wireless communication functionalities, facilitating instantaneous surveillance and data gathering from the surrounding environment. WSNs are utilized across diverse domains, such as environmental monitoring, industrial automation, healthcare, smart agriculture, home automation, and beyond. Due to the inherent characteristics of WSNs they face many security challenges ranging from resource-based attacks, such as energy depletion or computational overload, to eavesdropping, interception, and tampering. Moreover, the dynamic and often ad-hoc deployment of sensors in varying environments increases their vulnerability to physical intrusion attacks, the distributed and collaborative nature of WSNs raises concerns about data integrity, as compromised nodes can potentially propagate misleading or malicious information throughout the network. In this article, we categorize WSN attacks, identifying vulnerabilities and corresponding mitigation strategies. We also explore current research directions in WSN security, emphasizing the challenges in addressing these issues.

The possible role of coherence in highly diluted and succussed aqueous solutions

The historical problem of potentized (homeopathic, spagiric and other) remedies deals with their chemical-physical plausibility, i.e.: a consistent physical (molecular or electromagnetic) description have not yet been worked out and shared in scientific contexts [1]. I think that this difficulty pertains to the "generally accepted view of condensed matter" (to quote our mourned Giuliano Preparata [2]) and water condensed phases. Until we stay attached to a local, corpuscular and short-ranged description of matter (and of water, mainly) we won't be able to conceive the emergence of complex collective dynamics and their phenomenological outcomes. These are engendered by non-trivial ground states of the aqueous system in consequence both of its intrinsic nature and of the treatments to which it is subjected during dynamization. In this lecture I'll try, through a Quantum Electro-Dynamic (QED) theoretical framework [3,4,5], to sketch out the main features which let us envision liquid water as a two-phase system, where coherence is the basis both for its condensedness and for its ability to maintain long-lasting and far-from-equilibrium states able to non-randomly evolve in time through dissipative dynamics, and to understand the physical nature and properties of potentized remedies. Further comments about a likewise important question will be shared: how and why living matter is able to respond to such a kind of (possibly therapeutic) stimulations? [6,7]

Dust-obscured Galaxies in the XMM-SERVS Fields: Selection, Multiwavelength Characterization, and Physical Nature

Dust-obscured galaxies (DOGs) are enshrouded by dust and many are believed to host accreting supermassive black holes (SMBHs), which makes them unique objects for probing the coevolution of galaxies and SMBHs. We select and characterize DOGs in the 13 deg2 XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS), leveraging the superb multiwavelength data—from X-rays to radio. We select 3738 DOGs at z ≈ 1.6–2.1 in XMM-SERVS, while maintaining good data quality without introducing significant bias. This represents the largest DOG sample with thorough multiwavelength source characterization. Spectral energy distribution modeling shows DOGs are a heterogeneous population consisting of both normal galaxies and active galactic nuclei (AGNs). Our DOGs are massive ( logM⋆/M☉≈10.7-11.3 ), 174 are detected in X-rays, and they are generally radio-quiet systems. X-ray detected DOGs are luminous and are moderately to heavily obscured in X-rays. Stacking analyses for the X-ray undetected DOGs show highly significant average detections. Critically, we compare DOGs with matched galaxy populations. DOGs have similar AGN fractions compared with typical galaxy populations. X-ray detected DOGs have higher M ⋆ and higher X-ray obscuration, but they are not more star-forming than typical X-ray AGNs. Our results potentially challenge the relevance of the merger-driven galaxy-SMBH coevolution framework for X-ray detected DOGs.

Removal of <i>para</i>-Phenylenediamine (PPD) Dye from Its Aqueous Solution by Adsorption Using the Activated Carbon Nanoparticles

This study focused on the development of an efficient preparation method of activated carbon for the removal of para-phenylenediamine (PPD) dye in an aqueous solution. Walnut shells, a readily accessible biomass source in northern Iraq, were processed into activated carbon (AC). Several techniques, such as FTIR, XRD, and SEM, were applied to describe and study the surface of AC. According to XRD analysis, all the reflection peaks with the relative intensities of various planes indicate that the obtained particle size was around 7.63 nm. The influences of contact time, adsorbent, and other variables (the thermodynamic parameters for the influence of temperature) were calculated after studying the dosage and initial concentration. The effects of the change in the acidity functions and the increasing temperature were also studied. The results found that the best adsorption occurred in 120 min, with a 0.1 g adsorbent substance weight and pH 5. The adsorption rate was at its best at a temperature of 318 K. The best-recorded adsorption rate was obtained when applying the Langmuir and Freundlich isotherms, and the adsorption processes were of a physical nature.

About the attraction of hot particles in a cold bath

Motivated by questions in biological physics, we consider a model in which different Brownian particles interact with different thermostats. Computer simulations show that hot particles (i.e., interacting with the hot bath) attract each other when placed in an environment of colder particles (i.e., interacting with the cold thermostat). This paper presents a simple calculation that sheds light on the physical nature of this attraction.

The influence of external action on the dynamics of elastic, thermal and concentration waves propagation

This paper presents the nonlinear coupled mathematical model allowing investigating the interrelation between the mechanical, thermal and diffusion processes in solid body. The model takes into account the finiteness of relaxation times of mass and heat fluxes. This is of interest for dynamical processes with characteristic times comparable to relaxation times, when the changes in the temperature and impurity concentration are described by hyperbolic thermal conductivity and diffusion equations. Additionally, the model takes into account the temperature and concentration dependencies of the diffusion coefficients; it gives rise to additional nonlinearity. The model is thermodynamically consistent and follows from the nonlinear equations of the thermoelastic diffusion theory. The implicit difference scheme of second approximation order in time and spatial steps, linearization relatively to known time moment and double-sweep method are used for the numerical implementation of the equation system. Examples of interrelating wave propagating under external actions are considered. The results show that distortions in the strain/stress and temperature distributions appear due to the interaction between the phenomena of different physical nature. The specific rates of different physical processes are different. Although diffusion is the slowest of them all, the influence of the diffusion wave is reflected in stress and strain waves far beyond the diffusion wave front. It is shown that regardless of the external action character and impulse form, the influence of the considered processes on each other does not change, but the wave picture becomes much more complicated with increasing number of actions.

Rheological properties of water-oil emulsions of Archinskoe oil deposit

Relevance. The development of new methods for regulating the rheological properties of water-oil emulsion using thermal and chemical methods will allow reducing the viscosity of oil well products and energy consumption for pumping hydrocarbon mixtures. Aim. To determine the activation energy of viscous flow and particle sizes of the internal phase of the initial emulsion of the Archinskoe deposit and the emulsion with an introduced demulsifier. Methods. All experiments required to investigate the rheological properties of colloidal disperse systems were performed using HAAKE Viscotester iQ rotational viscometer. Results. Comparative experimental studies were carried out on the effect of the introduced demulsifier on the effective viscosity of the water-oil emulsion of the Archinskoe deposit. Laboratory-scale experiments were performed using the rotational viscometry, which allows one to evaluate the dependence of viscosity on shear rate and temperature. It was established that the studied samples are liquids with pronounced non-Newtonian properties, which are a consequence of the paraffinic nature of oil and its water-oil emulsion. The structure of nanoparticles of the dispersed phase of dehydrated oil and its emulsion is discussed and justified. Using the analytical Arrhenius–Frenkel–Eyring expression, which describes the dependence of viscosity on temperature and the physical and chemical nature of the liquid system, the results of viscometrical experiments were processed and the activation energies of viscous flow and the particle size of the inverse emulsion were calculated in the absence of a demulsifier and in its presence. Laboratory experiments have confirmed that for complete dehydration of oil well products, it is not enough to introduce only a demulsifier, but it also requires heating the emulsion to a temperature sufficient to melt and dissolve paraffin particles, which form a structural and mechanical barrier situated on the surface of the emulsion droplets.

Near-infrared Spectroscopy of the Sun and Solar Analog Star HD 76151: Compiling an Extensive Line List in the Y, J, H, and K Bands

Determining the physical nature of a star requires precise knowledge of its stellar atmospheric parameters, including effective temperature, surface gravity, and metallicity. This study presents a new atomic line list covering a broad spectral range (1–2.5 μm; YJHK bands) for iron (Fe) and α-elements (Ca, Mg, Ti, Si) to improve stellar parameter determination using near-infrared (NIR) spectroscopy. We highlight the limitations of existing line lists, stemming primarily from inconsistencies in oscillator strengths for ionized iron lines within the Apache Point Observatory Galactic Evolution Experiment DR17. The line list was validated using the high-resolution and high-quality disk-center NIR spectra of the Sun and its solar analog HD 76151. As a result of the spectroscopic analyses, the effective temperature of HD 76151 was calculated as 5790 ± 170 K, surface gravity as 4.35 ± 0.18 cgs, metal abundance as 0.24 ± 0.09 dex, and microturbulence velocity of 0.30−0.3+0.5 km s−1 by combining the optical and NIR line lists. A comparison of the model atmospheric parameters calculated for HD 76151 with the PARSEC isochrones resulted in a stellar mass of 1.053−0.068+0.056M⊙ , radius 1.125−0.011+0.035R⊙ , and an age of 5.5−2.1+2.5 Gyr. For the first time, kinematic and dynamical orbital analyses of HD 76151 using a combination of Gaia astrometric and spectroscopic data showed that the star was born in a metal-rich region within the solar circle and is a member of the thin disk population. Thus, the slightly metal-rich nature of the star, as reflected in its spectroscopic analysis, was confirmed by dynamical orbital analysis.

The Variability of Persistent Radio Sources of Fast Radio Bursts

Over 700 bright millisecond-duration radio transients, known as fast radio bursts (FRBs), have been identified to date. Nevertheless, the origin of FRBs remains unknown. Two repeating FRBs (FRB 20121102A and FRB 20190520B) have been verified to be associated with persistent radio sources (PRSs), making them the best candidates to study the nature of FRBs. Monitoring the variability in PRSs is essential for understanding their physical nature. We conducted 22 observations of the PRSs linked to FRB 20121102A and FRB 20190520B using the Karl G. Jansky Very Large Array, to study their variability. We have observed significant flux variability for the PRSs of FRB 20121102A and FRB 20190520B, with a confidence level exceeding 99.99%, based on the observations covering the longest timescale recorded to date. The observed variability of the two PRSs exhibits no significant difference in amplitude across both short and long timescales. We found that the radio-derived star formation rates of the two FRB hosts are significantly higher than those measured by the optical H α emissions, indicating that their host galaxies are highly obscured or most radio emissions are not from star formation processes. The observed timescale of PRS flux evolution constrained the magnetic field of FRB 20121102A with B ∥ ≳ 1 mG and FRB 20190520B with B ∥ ≳ 0.1 mG.

Reassessing green exercise research: unveiling methodological gaps and pathways for progress.

The present review critically assesses the nexus between physical activity, nature exposure and health benefits by analysing environmental measures in green exercise research. A Cochrane-inspired review of systematic studies exposes methodological gaps, emphasising the scarcity of long-term research and the lack of rigorous designed studies. It calls for more robust, varied research designs and improved environmental metrics. The findings advocate for longitudinal research to better comprehend the mental and physical health benefits of exposure to nature. Embracing an ecological-dynamic perspective is recommended to advance our understanding of the intricate connections between activity, environment, and well-being.

Quantum real-time evolution of entanglement and hadronization in jet production: Lessons from the massive Schwinger model

The possible link between entanglement and thermalization, and the dynamics of hadronization are addressed by studying the real-time response of the massive Schwinger model coupled to external sources. This setup mimics the production and fragmentation of quark jets, as the Schwinger model and quantum chromodynamics (QCD) share the properties of confinement and chiral symmetry breaking. By using simulations of quantum dynamics on classical hardware, we study the entanglement between the produced jets, and observe the growth of the corresponding entanglement entropy in time. This growth arises from the increased number of contributing eigenstates of the reduced density matrix with sufficiently large and close eigenvalues. We also investigate the physical nature of these eigenstates, and find that at early times they correspond to fermionic Fock states. We then observe the transition from these fermionic Fock states to mesonlike bound states as a function of time. In other words, we observe how hadronization develops in real time. At late times, the local observables at midrapidity (such as the fermion density and the electric field) approach approximately constant values, suggesting the onset of equilibrium and approach to thermalization. Published by the American Physical Society 2024

Influence of Transfer Epidemiological Processes on the Formation of Endemic Equilibria in the Extended SEIS Model

In the present paper, a modification of the standard mean-field model is considered, allowing for the description of the formation of a dynamic equilibrium between infected and recovered persons in a population of constant size. The key point of this model is that it highlights two-infection transfer mechanisms depending on the physical nature of the contact between people. We separate the transfer mechanism related directly to the movement of people (the so-called transport processes) from the one occurring at zero relative speed of persons (the so-called social contacts). Under the framework of a physical chemical analogy, the dependencies for the infection transfer rate constants are proposed for both purely transport and social mechanisms of spread. These dependencies are used in discussing the formation of quasi-stationary states in the model, which can be interpreted as endemic equilibrium states. The stability of such endemic equilibria is studied by the method of Lyapunov function.

Incidence of injury among male Varsity Cup Young Guns rugby players in South Africa.

The physical nature of the sport of rugby results in a high incidence of injury, even in university rugby, compared to other contact sport codes. Rugby Union lacks injury data focusing on university student-athletes, specifically in South Africa. The aim of the study was to determine the incidence of injury among male rugby players participating in the Varsity Cup Young Guns national rugby tournament. The study used a quantitative, cross-sectional, and correlational research design. A total of 252 rugby players, males aged 18 to 20 years, who played for their university rugby team in the 2022 Varsity Cup Young Guns national tournament were conveniently recruited to determine the incidence of overall, match, and training injuries (number of injuries/1000 hours) for the 2022 tournament. The overall injury incidence for all players was 9.5 injuries/1000 player-hours. The injury incidence for all players during matches was 136.5 injuries/1000 match-hours, whereas during training it was 0.6 injuries/1000 training-hours. The injury incidence was greater for backs than forwards (150.6 injuries/1000 match-hours vs. 124.1 injuries/1000 match-hours, respectively). The lower limb was the most commonly injured anatomical site with 36.6% (95% CI: 27.7-48.3%), while the common types of injuries were the joints (41.6%, 95% CI: 29.9-49.9%) and muscles (28.7%, 95% CI: 20.8-38.0%). A statistically significant association was found between the playing position and the phase of play in which injury occurred (χ2<inf>(1)</inf>=160.2; P=0.021). This study reported a high injury incidence, especially during matches, in the Varsity Cup Young Guns tournament. It is recommended that prospective, incidence-based studies be used to precisely determine the incidence, nature, severity and mechanisms of injury. An injury surveillance system should be implemented, specifically within Varsity Cup rugby to inform, support, and improve current injury prevention strategies.

INFORMATION MODEL FOR SELECTING THE OPTIMAL SPATIAL FORM OF PARTS

A complex of interrelated methods and means of analysis, clustering, segmentation and classification of objects on images obtained by sensors of different physical nature (with the help of modern methods of radiography, computer and magnetic resonance imaging) is proposed, which will allow modeling the optimal form of a bone substitute with functional properties by CAD/CAM/CAE design methods, depending on the anatomical data, the nature and localization of the cavity bone defect, its size, load conditions and patterns of bone tissue neoplasm. Methods for making multi-criteria decisions have been developed, which will allow for their implementation for a wide range of optimization tasks of researching the correlation of the shape and size of porosity with indicators of the stress-deformed state of bone substitutes in order to maintain the structural integrity of the biomaterial in the process of regeneration of hard tissue.

Measuring Sub-Kelvin Variations in Stellar Temperature with High-resolution Spectroscopy

The detection of stellar variability often relies on the measurement of selected activity indicators, such as coronal emission lines and nonthermal emissions. On the flip side, the effective stellar temperature is normally seen as one of the key fundamental parameters (with mass and radius) to understanding the basic physical nature of a star and its relation with its environment (e.g., planetary instellation). We present a novel approach for measuring disk-averaged temperature variations to sub-Kelvin accuracy inspired by algorithms developed for precision radial velocity (pRV). This framework uses the entire content of the spectrum, not just preidentified lines, and can be applied to existing data obtained with high-resolution spectrographs. We demonstrate the framework by recovering the known rotation periods and temperature modulation of Barnard star and AU Mic in data sets obtained in the infrared with SPIRou at CHFT and at optical wavelengths on ϵ Eridani with HARPS at ESO 3.6 m telescope. We use observations of the transiting hot Jupiter HD189733b, obtained with SPIRou, to show that this method can unveil the minute temperature variation signature expected during the transit event, an effect analogous to the Rossiter–McLaughlin effect but in temperature space. This method is a powerful new tool for characterizing stellar activity, and in particular temperature and magnetic features at the surfaces of cool stars, affecting both pRV and transit spectroscopic observations. We demonstrate this method in the context of high-resolution spectroscopy but it could be used at lower resolution.