Energy-dependent Behavior Research Articles

Investigation of the electromagnetic shielding efficiency of FeB and Fe2B: ab-initio calculations

Abstract The electromagnetic (EM) pollution that we are exposed to in our daily lives has reached levels that threaten the health of living organisms and the stable operation of sensitive systems. The most effective way to protect against this pollution is to create isolated areas framed with shielding materials that can minimize the transmission of EM radiation. The development of shielding materials with high physical endurance against external factors to meet the needs of various sectors remains a popular research topic. This process, which started with metal plates, has continued with the development of doped polymers and composite materials. In recent years, materials with 2D structures have been developed. In this study, the shielding effectiveness (SE) of FeB and Fe2B nanostructures are revealed using ab initio calculations in Perdew–Burke–ErnzerhofSol scheme. SE has been widely figuring out via optical properties which are strongly related to mechanical and electronic properties herewith magnetic phases. The ferrimagnetic FeB and Fe2B nanostructures are considered. Besides, we focus on the thickness and photon energy dependent behavior along various projections. The findings demonstrate shielding performance at levels of >20 dB. Although both materials show similar shielding performance, it is observed that Fe2B is promising when compared to FeB. This study demonstrates that FeB and Fe2B, members of the MBene family, are promising materials not only because of their superior physical and chemical properties but also because of their shielding performance.

Polarization effects of hot nuclear matter on the fusion of heavy ions

Within the framework of the modified density-dependent Seyler–Blanchard approach in the [Formula: see text] approximation, the polarization effects of hot nuclear matter (PEHNM) are investigated on the fusion process of 16 different colliding systems in the mass range [Formula: see text]. In order to calculate the nucleus–nucleus potential, we use the double-folding (DF) model supplemented with the thermal effects of compound nucleus and also a repulsive potential that takes into account the incompressibility of the nuclear matter. The calculations of the fusion cross-sections are performed based on the couplings to the low-lying [Formula: see text] and [Formula: see text] vibrational states in both target and projectile. The sensitivity of sub-barrier fusion cross-sections to the polarization effects is evident from this study. The obtained results reveal that the modified form of the DF potential in the presence of the PEHNM appropriately reproduces the energy-dependent behavior of the experimental fusion cross-sections for the studied reactions. The role of the polarization effects on the fusion barriers as well as the inner part of the potential is also discussed.

Generalized boost transformations in finite volumes and application to Hamiltonian methods

The investigation of hadron interactions within lattice QCD has been facilitated by the well-known quantisation condition, linking scattering phase shifts to finite-volume energies. Additionally, the ability to utilise systems at finite total boosts has been pivotal in smoothly charting the energy-dependent behaviour of these phase shifts. The existing implementations of the quantization condition at finite boosts rely on momentum transformations between rest and moving frames, defined directly in terms of the energy eigenvalues. This energy dependence is unsuitable in the formulation of a Hamiltonian. In this work, we introduce a novel approach to generalise the three-momentum boost prescription, enabling the incorporation of energy-independent finite-volume Hamiltonians within moving frames. We demonstrate the application of our method through numerical comparisons, employing a phenomenological ππ scattering example.

Computation insights of kagome structure for probing electronic and thermodynamic properties by applying external factors such as strain, spin-orbital coupling, and external magnetic field

In this study, we explored the electronic properties of a two-dimensional (2D) kagome lattice in the presence of an external magnetic field, spin-orbit coupling (SOC), and strain. Our focus was on investigating the energy-dependent behavior of the electronic heat capacity and paramagnetic spin susceptibility in response to changing factors. Employing the Green's function approach, we successfully determined the energy dependence of the electronic heat capacity and paramagnetic susceptibility using the tight-binding model. Notably, at low energies, the electronic heat capacity almost reaches the Schottky anomaly peak, while the paramagnetic susceptibility sharply decreases. Furthermore, we conducted a detailed investigation of the energy-dependent paramagnetic susceptibility and electronic heat capacity of a kagome lattice monolayer, considering the influences of SOC and magnetic field factors. Our investigation of the density of states (DOS) in the presence of SOC suggests that semimetal-to-insulator phase transitions occur. Additionally, throughout our study, we observed variations in the DOS spectrum, indicating the influence of both compressive and tensile strains. We found that these alterations, along with the splitting of levels under different conditions, led to changes in the material's electrical properties.

Threshold anomalies in 9Be + 12C

The extended optical model is used to simultaneously analyze the elastic scattering and fusion data for the weakly-bound system of 9Be + 12C in the low-energy region. Dynamic polarization potentials UF, UD, associated with fusion and direct couplings, respectively, are introduced. Corresponding fitting parameters leading to dispersive potentials are found, which provide good simultaneous descriptions of elastic and fusion data. The energy-dependent behavior of the polarization potentials establishes a striking difference with respect to that observed for weakly bound projectiles, including 9Be, on medium- and heavy-mass targets. Contrary to similar analyses made on weakly-bound systems, the real part of UD is found to be attractive in the present case. The observed behavior is discussed.

Behaviour of 27-Day and 13.5-Day Periodicities in Galactic Cosmic Particles as Observed by Spacecraft and Neutron Monitors During Different Solar Polarity Cycles

An analysis has been made of the behaviour of the 27-day and 13.5-day periodicities in proton, C, and O galactic-cosmic-ray (GCR) particles at different energies as observed by the Advanced Composition Explorer (ACE) and SOHO (Solar and Heliospheric Observatory) spacecraft during both Solar Cycles 23 and 24. In addition, the behaviour of the 27-day and 13.5-day periods in the solar-wind-modulation parameter zeta = BIMF × VSW has been investigated during the same time interval to determine the existence of a possible solar-polarity dependence. Ground-based neutron-monitor (NM) observations, corresponding to different rigidity cutoff [RC] parameters, were also studied to determine the temporal behaviour of both the 27-day and 13.5-day periods during Cycles 23 and 24, revealing a statistically significant solar-polarity correlation. The Lomb–Scargle periodogram technique has been employed to extract spectral information from the above-mentioned observations for each individual year from 2001 – 2009 (Cycle 23) and 2010 – 2019 (Cycle 24). Daily mean energetic ACE and SOHO particle measurements are used to identify how both the 27-day and 13.5-day periodicities vary during each individual year during these cycles as a function of particle mean energy. This spectral analysis of proton, C, and O galactic-cosmic-particle data at different energies revealed that both the 27-day and 13.5-day periods are stronger during the minimum of Solar Cycle 24/25 when A > 0 (solar dipole pointing North) in comparison to the minimum of Cycle 23/24 when A < 0 (solar dipole pointing South) at certain energy levels. This showed a particularly strong energy-dependent behaviour for both periodicities. This article reports for the first time an annual time- and energy-dependent behaviour of both the 27-day and 13.5-day periodicities in daily-mean galactic cosmic particles observed by spacecraft and ground-based neutron monitors during consecutive Solar Cycles 23 and 24, corresponding to opposite solar-magnetic-field orientations. Periodicity behaviour in heliospheric solar-wind data corroborate these results in general.

Influence of Fe2O3@reduced graphene oxide nanocomposite on the structural, morphological, and optical features of the polyvinyl alcohol films for optoelectronic applications

Polyvinyl alcohol (PVA) films doped with Fe2O3-reduced graphene oxide (rGO) nanoparticles (NPs) were prepared using a casting-method. Fe2O3 NPs were synthesized via the hydrothermal process, and then Fe2O3 NPs were decorated on the graphene oxide (GO) sheets, where the GO was transferred to rGO during the sonication process. The obtained films were characterized using XRD and FTIR techniques. Optical absorption and transmission data were recorded via a UV–visible spectrophotometer and used to estimate various optical parameters. Increasing the amount of doped Fe2O3-rGO NPs in PVA decreased the ability of the prepared nanocomposites to allow visible light to pass through them. Solar material protection factor (SMPF) of PVA (11.93%) improved to 99.3%, corresponding to 2 wt% of Fe2O3-rGO NPs doped in the host matrix. The calculated values of the average refractive index are 2.18, 2.25, 2.36, 2.46, and 2.58, corresponding to 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, and 2 wt% of Fe2O3-rGO NPs doped in PVA. Therefore, the average refractive index showed a dependence on Fe2O3-rGO NPs. Low energy region (E < 2.4 eV) showed dielectric relaxation time- energy dependent behavior, whereas the high energy region (E > 2.4 eV) displayed dielectric relaxation time- energy independent behavior. Increasing the content of the doped NPs in PVA resulted in lowering the surface and volume energy loss.

Study of strange quark density fluctuations in Au + Au Collisions at $$\sqrt{\textrm{s}_{_{\textrm{NN}}}}$$ = 7.7–200 GeV from AMPT Model

The strangeness production is an important observable to study the QCD phase diagram. The yield ratios of strange quark can be helpful to search for the QCD critical end point (CEP) and/or first-order phase transition. In this work, we studied the production of $$K^{\pm }$$ , $$\Xi ^-({\bar{\Xi }}^{+})$$ , $$\phi $$ and $$\Lambda ({\bar{\Lambda }})$$ in Au + Au collisions at $$\sqrt{\textrm{s}_{_{\textrm{NN}}}}$$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, and 200 GeV from A Multi-Phase Transport model with string melting version (AMPT-SM). We calculated the invariant yield of these strange hadrons using a different set of parameters compared to those reported in earlier studies and also by varying the hadronic cascade time ( $$t_{max}$$ ) in the AMPT-SM model. We also calculated the yield ratios, $${\mathcal {O}}_{K^{\pm }-\Xi ^{-}({\bar{\Xi }}^{+})-\phi -\Lambda (\bar{\Lambda })}$$ which are reported as sensitive to the strange quark density fluctuations and found that the AMPT-SM model fails to describe the non-monotonic trend observed by the experimental data. The negative particle ratio are found to be higher than the ratio of positive particles which is consistent with the experimental data. A significant effect is also seen on these ratios by varying the $$t_{max}$$ . For a crossover transition between the Quark-Gluon Plasma (QGP) and hadronic matter, the double yield ratios considered in the present study based on AMPT-SM model do not show any non-monotonic behaviors and thus providing a baseline for the search of CEP, because there is no first-order or second-order phase transition in the AMPT model. The more realistic equation of state based dynamical modeling is still required for the heavy-ion collisions in order to extract the definite physics conclusion about the non-monotonic energy dependence behavior.

Signatures of the exciton gas phase and its condensation in monolayer 1T-ZrTe2

The excitonic insulator (EI) is a Bose-Einstein condensation (BEC) of excitons bound by electron-hole interaction in a solid, which could support high-temperature BEC transition. The material realization of EI has been challenged by the difficulty of distinguishing it from a conventional charge density wave (CDW) state. In the BEC limit, the preformed exciton gas phase is a hallmark to distinguish EI from conventional CDW, yet direct experimental evidence has been lacking. Here we report a distinct correlated phase beyond the 2×2 CDW ground state emerging in monolayer 1T-ZrTe2 and its investigation by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). The results show novel band- and energy-dependent folding behavior in a two-step process, which is the signatures of an exciton gas phase prior to its condensation into the final CDW state. Our findings provide a versatile two-dimensional platform that allows tuning of the excitonic effect.

Charm and beauty isolation from heavy flavor decay electrons in p+p and Pb+Pb collisions at [formula omitted] = 5.02 TeV at LHC

We present an analysis on the heavy flavor hadron decay electrons with charm and beauty contributions decomposed via a data driven method in p+p and Pb+Pb collisions at sNN = 5.02 TeV at LHC. The transverse momentum pT spectra, nuclear modification factor RAA and azimuthal anisotropic flow v2 distributions of electrons from charm and beauty decays are obtained. We find that the electron RAA from charm (RAAc→e) and beauty (RAAb→e) decays are suppressed at pT>2.0 GeV/c in Pb+Pb collisions, which indicates that charm and beauty interact with and lose their energy in the hot-dense medium. A less suppression of RAAb→e than RAAc→e at 2.0<pT<8.0 GeV/c is observed, which is consistent with the mass-dependent partonic energy loss scenario. A non-zero electron v2 from beauty decays (v2b→e) is observed and in good agreement with ALICE measurement. At low pT from 1.0 to 3.0 GeV/c, a discrepancy between RHIC and LHC results is observed with an 85% confidence level, which might be a possible hint of an energy-dependent behavior of beauty quarks reacting with the medium created in heavy-ion collisions. At 3.0<pT<7.0 GeV/c, v2b→e deviates from a number-of-constituent-quark (NCQ) scaling hypothesis, which favors that beauty quark is unlikely thermalized in heavy-ion collisions at LHC energy.

Universal Thermal Entanglement of Multichannel Kondo Effects.

Quantum entanglement between an impurity and its environment is expected to be central in quantum impurity problems. We develop a method to compute the entanglement in spin-1/2 impurity problems, based on the entanglement negativity and the boundary conformal field theory (BCFT). Using the method, we study the thermal decay of the entanglement in the multichannel Kondo effects. At zero temperature, the entanglement has the maximal value independent of the number of the screening channels. At low temperature, the entanglement exhibits a power-law thermal decay. The power-law exponent equals two times of the scaling dimension of the BCFT boundary operator describing the impurity spin, and it is attributed to the energy-dependent scaling behavior of the entanglement in energy eigenstates. These agree with numerical renormalization group results, unveiling quantum coherence inside the Kondo screening length.

Heavy-ion fusion cross sections in the barrier and high-energy regions: Signature of energy dependence in the repulsive core potential

The effect of incompressibility of cold nuclear matter (CNM) on the high-energy fusion data of the 26Mg+248Cm, 36S+238U, 48Ca+208Pb, 50Ti+209Bi and 40,48Ca+238U colliding systems with 1152≤Z1Z2≤1840 has been analyzed using coupled-channels (CC) calculations. To apply the effect of saturation property of nuclear matter, we use the M3Y double-folding model which is corrected with a repulsive term. The repulsive parameters are adjusted to provide an optimum fit to the available experimental fusion cross sections. For each of the 26Mg+248Cm, 36S+238U, 48Ca+208Pb colliding systems, the best fit to the measured fusion cross sections at high energies is achieved using the CC calculations based on the M3Y+Repulsion potential with a constant value for the strength of the repulsive contact term. While focusing on the heavy-ion fusion reactions existing in the mass range Z1Z2>1800 reveals that it is necessary to consider an energy-dependent behavior for the repulsive parameters. When these conditions are imposed on entrance channel potential, it is possible to obtain an excellent description of the fusion data for 50Ti+209Bi, 40Ca+238U, and 48Ca+238U reactions. Our findings indicate that the extracted values of the strength Vrep of the repulsive contact term increase with increasing incident energy Ec.m.. In addition, we conclude that the repulsive part of the density distribution becomes more diffused with an increase in bombarding energy.

Shock compression-induced enhancement of stimulated Raman scattering in heavy water

Stimulated Raman Scattering (SRS) of shock-compressed liquid heavy water was observed using a Nd:YAG laser in both the forward and backward directions of the laser beam. SRS spectra exhibited different characteristic features at weak and intense pump energies. As for the intense pump energy, the main SRS peak occurred at approximately 2400 cm −1 and subsequently shifted to a lower frequency. Interestingly, some new peaks were observed in both directions. Specifically, a lower frequency peak close to 2200 cm −1 and 2nd-order anti-Stokes peaks were observed in the backward direction, which further indicated that an ice-VII cubic structure was formed under shock compression conditions. In addition, the normalized intensity ratio of the two main peaks exhibited quite different energy-dependent behaviors. The results demonstrated that the shock-induced high pressure environment significantly enhanced SRS. The results could be attributed to the enhancement effect of Kerr self-focusing and the competitive Backward Stimulated Brillouin Scattering (BSBS) and Forward SRS (FSRS) processes.

Nearby source interpretation of differences among light and medium composition spectra in cosmic rays

Recently the AMS-02 reported the precise measurements of the energy spectra of medium-mass compositions (Neon, Magnesium, Silicon) of primary cosmic rays, which reveal different properties from those of light compositions (Helium, Carbon, Oxygen). Here we propose a nearby source scenario, together with the background source contribution, to explain the newly measured spectra of cosmic ray Ne, Mg, Si, and particularly their differences from that of He, C, O. Their differences at high energies can be naturally accounted for by the element abundance of the nearby source. Specifically, the abundance ratio of the nearby source to the background of the Ne, Mg, Si elements is lower by a factor of $\sim1.7$ than that of the He, C, O elements. Such a difference could be due to the abundance difference of the stellar evolution of the progenitor star or the acceleration process/environment, of the nearby source. This scenario can simultaneously explain the high-energy spectral softening features of cosmic ray spectra revealed recently by CREAM/NUCLEON/DAMPE, as well as the energy-dependent behaviors of the large-scale anisotropies. It is predicted that the dipole anisotropy amplitudes below PeV energies of the Ne, Mg, Si group are smaller than that of the He, C, O group, which can be tested with future measurements.

Rainbow spacetime from a nonlocal gravitational uncertainty principle

The occurrence of spacetime singularities is one of the peculiar features of Einstein gravity, signalling limitation on probing short distances in spacetime. This alludes to the existence of a fundamental length scale in nature. On the contrary, the Heisenberg quantum uncertainty relation seems to allow for probing arbitrarily small length scales. To reconcile these two conflicting ideas in line with a well-known framework of quantum gravity, several modifications of Heisenberg algebra have been proposed. However, it has been extensively argued that such a minimum length would introduce nonlocality in theories of quantum gravity. In this letter, we analyze a previously proposed deformation of the Heisenberg algebra (i.e., ) for a particle confined in a box subjected to a gravitational field. For the problem in hand, such deformation seems to yield an energy-dependent behavior of spacetime in a way consistent with gravity's rainbow, hence demonstrating a connection between non-locality and gravity's rainbow.

Identifying the radiative components responsible for quasi-periodic oscillations of black hole systems

ABSTRACT While the dynamical origin of the variability observed in Galactic black hole systems, such as quasi-periodic oscillations (QPOs), is still a matter of debate, insight into the radiative components responsible for such behaviour can be obtained by studying their energy-dependent temporal behaviour. In particular, one needs to ascertain which variations of the parameters of the best-fitting time-averaged spectral components reproduce the observed energy-dependent fractional rms and time-lags. However, to obtain meaningful interpretation, the standard spectral component parameters have to be recast to physically relevant ones. Then, the energy-dependent temporal variations that their fluctuations will cause, needs to be predicted and compared with observations. In this work, we describe a generic method to do this and apply the technique to the ∼3–4 Hz QPOs observed in the black hole system GRS 1915+105 as observed by AstroSat where the time-averaged spectra can be represented by emission from a truncated disc and hot thermal Comptonizing coronae in the inner regions. We find that the QPOs and their harmonic can be explained in terms of correlated local accretion rate variations in the disc, the truncated disc radius, the optical depth and the heating rate of the coronae with time-delays between them. We highlight the potential of such techniques to unravel the radiative process responsible for variability using high-quality spectral and temporal data from AstroSat and NICER.

Constraining the particle production mechanism in Au+Au collisions at sNN=7.7 , 27, and 200 GeV using a multiphase transport model

We study the production of pions, kaons, and (anti)protons in A Multi Phase Transport (AMPT) Model in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 27, and 200 GeV. We present the centrality and energy dependence of various bulk observables such as invariant yields as a function of transverse momentum $p_T$, particle yields $dN/dy$, average transverse momentum $\langle p_T \rangle$, and various particle ratios, and compare them with experimental data. Both default and string melting (SM) versions of the AMPT model are used with three different sets of initial conditions. We observe that neither the default nor the SM version of the model could consistently describe the centrality dependence of all observables at the above energies with any one set of initial conditions. The energy dependence behavior of the experimental observables for 0--5\% central collisions is in general better described by the default AMPT model using the modified HIJING parameters for Lund string fragmentation and 3mb parton scattering cross-section. In addition, the kaon production as well as the $K/\pi$ ratio at 7.7 GeV are under predicted by the AMPT model.

Updated Spin and Orbital Parameters and Energy Dependent Pulse Behaviors of the Accreting Millisecond X-Ray Pulsar IGR J17591–2342

Abstract We present our work in updating the spin and orbital parameters for the newly discovered accreting millisecond X-ray pulsar (AMXP) IGR J17591–2342 through pulsar timing and analyzing its energy dependent pulse behaviors. The data being analyzed were collected by Neutron Star Interior Composition ExploreR, which observed this AMXP from 2018 August to October. Using the pulse arrival time delay technique, more accurate spin and orbital parameters were evaluated. From the measured spin frequency derivative, it is estimated that the magnetic field of the neutron star in IGR J17591–2342 is approximately 4 × 108 G. Precise pulse profiles can be made using the updated spin and orbital parameters. The soft phase lag phenomenon that is usually seen in other AMXPs is also observed from ∼4 to 12 keV with a value of 0.06 cycles (1.14 μs). Additionally, the pulsed fractional amplitude increases from 1 to ∼5 keV and then decreases for higher energy bands. We found that these phenomena, as well as the energy spectrum, can be explained by the two-component model with a relatively strong blackbody component and an additional unpulsed disk blackbody component.

Probing gaseous molecular structure by molecular-frame photoelectron angular distributions.

Carbon 1s photoelectron angular distributions of an iodomethane molecule were measured relative to the recoil-frame determined by the momentum correlation between I+ and CH3 + at photoelectron energies of 3, 6.1, and 12 eV. The energy dependent behavior of the recoil-frame photoelectron angular distributions is reproduced reasonably well by the time-dependent density functional theory with B-spline methods. We discuss potential applications of the fully differential photoelectron angular distribution measurements in the molecular frame to three-dimensional molecular structural determinations identifying the directions and lengths of the bonds.

Cross-section determination for one- and two-photon absorption of cobalt at hard-x-ray energies

For incident x-ray energies below the core level ionization threshold, one-photon absorption (OPA) leads to off-resonant x-ray excitations that are mediated by a virtual intermediate electronic state. In the linear regime of x-ray interaction, this intermediate state may decay radiatively and the maximum energy of the emitted photon is given by the initial and final atomic state as well as the energy of the incident photon. In the nonlinear excitation regime, however, this intermediate state may be depleted by a second x-ray absorption process as described in the sequential two-photon absorption (TPA) mechanism. Since the same intermediate state is involved in the OPA and TPA processes, the cross-section values for OPA and TPA are interconnected. We report on the determination of cross-section values for off-resonant excitation conditions, and show how the data can be used for estimating the TPA cross section in the sequential absorption mechanism. The determined off-resonant cross sections for cobalt exhibit a Lorentz-like energy-dependent behavior allowing for an energy-dependent description of the OPA and TPA cross sections with semiempirical models. The dependence of TPA cross sections on atomic number is discussed and different scaling laws are investigated. The effect of the lifetimes of a virtual intermediate state is also studied in relation to the incidence x-ray energy.