Energy W0 Research Articles

Investigating early dark energy with new observations

This paper mainly presents updated constraints on several types of early dark energy (EDE) models proposed by V. Pettorino et al. using observations of cosmic microwave background radiation (CMB) from Planck satellite, the Pantheon Type Ia supernovae (SNIa) sample, and baryon acoustic oscillation (BAO) measurements. The results yield stringent upper limits on the constant EDE fraction parameter Ωe. While the present equation of state (EoS) of dark energy w0 in the EDE1 model suggests a mild tendency towards a value less than −1, these models remain compatible with the ΛCDM scenario. Partly as a result of this slight tendency towards phantom late-time physics, EDE1 model supports a higher Hubble constant value, potentially narrowing the Hubble tension gap. The global fitting results also align with the notion that the constraint ability on Ωe weakens when dark energy is present only over a limited period after last scattering. Furthermore, by using the formalism of Fisher information matrix, we forecast uncertainties in the measured parameters of EDE models from the next-generation “Stage 4” CMB (CMB-S4) experiment. Forecasted precision of w0 and Ωe surpasses certain prior works, and most other basic parameters exhibit significantly higher limit precision compared to Planck 2018 results within the ΛCDM framework. To confirm the presence of EDE within the EDE1∼EDE4 parameterization frameworks, further advancements in observations are crucial.

Multimessenger Detection Rates and Distributions of Binary Neutron Star Mergers and Their Cosmological Implications

Abstract Gravitational wave (GW) events, produced by the coalescence of binary neutron stars (BNSs), can be treated as the standard sirens to probe the expansion history of the universe, if their redshifts can be determined from electromagnetic (EM) observations. For the high-redshift (z ≳ 0.1) events, the short γ-ray bursts (sGRBs) and the afterglows are always considered as the primary EM counterparts. In this paper, by investigating various models of sGRBs and afterglows, we discuss the rates and distributions of the multimessenger observations of BNS mergers using GW detectors in the second-generation (2G), 2.5G, and 3G era with detectable sGRBs and afterglows. For instance, for the Cosmic Explorer GW detector, the rate is about 300–3500 yr−1 with a GECAM-like detector for γ-ray emissions and an LSST/WFST detector for optical afterglows. In addition, we find that these events have redshifts z ≲ 2 and inclination angles ι ≲ 20°. These results justify the rough estimation in previous works. Considering these events as standard sirens to constrain the equation-of-state parameters of dark energy w 0 and w a , we obtain the potential constraints of Δw 0 ≃ 0.02–0.05 and Δw a ≃ 0.1–0.4.

Impacts of solvent electric dipole and ion valency on energy storage in ultrananoporous supercapacitor: An ising model study

A four-state BEG model is constructed to investigate effects of electric dipole of solvent molecule and ion valency on differential capacitance Cd and energy storage Eof the supercapacitor based on electrical double layer inside an ultranano-cylindrical pore about the size of the ions and solvent. In the model, existence of voids is permitted, solvent molecule is modelled as neutral hard sphere with an electrical dipole moment and ions are described by the primitive model; all electrostatic interactions between cation, anion, and polarized charges on the solvent molecule are limited to the nearest neighbor interactions. The present investigation is limited to weak solvent-solvent electrostatic interaction in comparison to that of the solvent-ion and ion-ion. New effects are found and summarized as follows. (i) There appears a zero Cd and zero E platform around the zero surface potential, which widens with the increase of the solvent transfer energy w0 and moves to positive surface potential side with replacement of the monovalent cation by bivalent cation. (ii) The saturated surface potential |Usat|, beyond which Cd reduces to zero and E reaches its saturation value Esat, is positively correlated with the w0 value. The correlation strength reduces with the counter-ion valence. (iii) For appropriate positive w0 value, both |Usat| and Esat always increase with the solvent polarized charge valence b and dipole length l whether the electrolyte type is +1: 1 or +2: 1; whereas for negative w0 value, the value and l value effects are very small and graphically unobservable. (iv) Presence of bivalent counter-ions causes an increase of the Cd peak strength and Esat value, whereas the presence of bivalent co-ion almost does not bring graphically observed effect. (v) Within the ranges of the b and l values considered, the energy storage is raised by increasing the solvent electrical dipole moment (whether by increasing b valueb or l value) without paying for the cost of high surface potential applied.

The formation of amplitude spectra in X-ray pixel detectors made of gallium arsenide.

This study aims to analyse energy spectra formation in semiconductor X-ray pixel detectors using a simple experimental method. The calculations were performed for the pixel detectors made of high-resistivity gallium arsenide compensated by chromium GaAs (Cr). A peculiar feature of these detectors is an extremely short lifetime of the holes. When using ordinary detectors with planar electrodes the spectra with high energy resolution could not be observed. In this study, the shape of amplitude spectra of gamma rays were calculated with energy W0 = 60 and 17 keV. The calculations were performed for the pixel detector of GaAs (Cr) with the thickness of d = 500μm and pixel pitch of 50μm. The mobility of electrons and holes were assumed to be μn = 3000 cm2/Vs, μp = 300 cm2/Vs, and the lifetimes were τn = 20 ns and τp = 1 ns, respectively. It was demonstrated that in the pixel detector, where there was practically no collection of holes and the amplitude spectra occurred with the energy resolution of 3.5 keV. The calculations show that energy spectra of the pixel detectors has a high energy resolution at an appropriate polarity applied bias voltage. The calculation results were conformed by the experimental data.

Probing cosmology with weak lensing selected clusters. II. Dark energy and f(R) gravity models

Abstract Ongoing and future wide-field galaxy surveys can be used to locate a number of clusters of galaxies with cosmic shear measurement alone. We study constraints on cosmological models using statistics of weak lensing selected galaxy clusters. We extend our previous theoretical framework to model the statistical properties of clusters in variants of cosmological models as well as in the standard ΛCDM model. Weak lensing selection of clusters does not rely on conventional assumptions such as the relation between luminosity and mass and/or hydrostatic equilibrium, but a number of observational effects compromise robust identification. We use a large set of realistic mock weak lensing catalogs as well as analytic models to perform a Fisher analysis and make a forecast for constraining two competing cosmological models, the wCDM model and f(R) model proposed by Hu and Sawicki (2007, Phys. Rev. D, 76, 064004), with our lensing statistics. We show that weak lensing selected clusters are excellent probes of cosmology when combined with cosmic shear power spectrum even in the presence of galaxy shape noise and masked regions. With the information from weak lensing selected clusters, the precision of cosmological parameter estimates can be improved by a factor of ∼1.6 and ∼8 for the wCDM model and f(R) model, respectively. The Hyper Suprime-Cam survey with sky coverage of 1250 degrees squared can constrain the equation of state of dark energy w0 with a level of Δw0 ∼ 0.1. It can also constrain the additional scalar degree of freedom in the f(R) model with a level of |fR0| ∼ 5 × 10−6, when constraints from cosmic microwave background measurements are incorporated. Future weak lensing surveys with sky coverage of 20000 degrees squared will place tighter constraints on w0 and |fR0| even without cosmic microwave background measurements.

Spectral properties of Holstein and breathing polarons

We calculate the spectral properties of the one-dimensional Holstein and breathing polarons using the self-consistent Born approximation. The Holstein model electron-phonon coupling is momentum independent while the breathing coupling increases monotonically with the phonon momentum. We find that for a linear or tight binding electron dispersion: i) for the same value of the dimensionless coupling the quasiparticle renormalization at small momentum in the breathing polaron is much smaller, ii) the quasiparticle renormalization at small momentum in the breathing polaron increases with phonon frequency unlike in the Holstein model where it decreases, iii) in the Holstein model the quasiparticle dispersion displays a kink and a small gap at an excitation energy equal to the phonon frequency w0 while in the breathing model it displays two gaps, one at excitation energy w0 and another one at 2w0. These differences have two reasons: first, the momentum of the relevant scattered phonons increases with increasing polaron momentum and second, the breathing bare coupling is an increasing function of the phonon momentum. These result in an effective electron-phonon coupling for the breathing model which is an increasing function of the total polaron momentum, such that the small momentum polaron is in the weak coupling regime while the large momentum one is in the strong coupling regime. However the first reason does not hold if the free electron dispersion has low energy states separated by large momentum, as in a higher dimensional system for example, in which situation the difference between the two models becomes less significant.

Minimum energy of a free electron in inert gases

The properties of the minimum energy W of a low-energy free electron in an inert gas are discussed. This quantity is one of the basic characteristics of the electron in problems of the formation of various charged clusters (bubbles or compacts) in low-dimensional electronic states along interfaces. A relation between the energy W and a similar energy W0 determined in the so-called optical approximation, where the energy W0 is proportional to the gas density ng, has been obtained. Comparison makes it possible to determine the ng dependence of the scattering length a0 introduced in the “optical” description of the gaseous medium and to reveal the conditions under which a0(ng) may change sign, which behavior, by definition, is beyond the framework of the optical approximation and is observed experimentally.

Determination of the time-dependent plastic properties of solids by dynamic nanoindentation

A new method is described to determine the time-dependent elastoplastic and dissipative properties of solids in nanovolumes by recording the instantaneous values of the stress and depth of penetration of a rigid indenter. Measurements are also made of the energy W 1 supplied to the indenter, the energy U dissipated in the insertion process, and the energy W 0 returned to the indenter on unloading. Results of measurements of the dynamic microhardness and also of the energies W 0 and U for NaCl crystals are presented as functions of the duration of contact between the indenter and the surface for times between 1 ms and 10 s.

Relativistic Collisionless Clusters with Arbitrarily Large Central Redshift

Some previous results obtained by Rasio, Shapiro, & Teukolsky are analyzed within the theoretical framework developed by Bisnovatyi-Kogan et al. The Rasio et al. configurations are shown to belong to a special family of configurations of equilibrium for relativistic clusters with a constant value of the central cutoff energy W0 114. A new classification of the configurations of equilibrium into three different regimes in the central redshift versus temperature diagram is proposed. The possible confrontation of these results with observational parameters is outlined briefly.

A theory for the width of the Coulomb gap

The results of two different calculations of the mean width Eg of the Coulomb gap are presented. The calculations are performed for the 'lattice model' used by Efros and Shklovskii (1975) in which the fractional site occupation K and the disorder energy W0 are parameters which may be varied independently. The authors determine approximations to the ground state first by stabilising the system against single-electron transfers, and second by direct minimisation of the total energy. Eg is found to depend on W0 as Eg varies as Ec((Ec/W0+Ec))1(d-1)/ where d is the dimensionality, and is either two or three. The dependence on K of Eg differs slightly for the two methods.

Roughening transition of high-index crystal faces: the case of copper

The thermal variation of atomic beam diffraction intensities on (1, 1, 2n + 1) faces of Cu is discussed for large n. the dramatic decrease of intensity at about 600K is attributed to a roughening transition, above which the steps are fuzzy. The steps are assumed to repel themselves with a repulsion energy proportional to (2n+1)-2, of elastic or electrostatic nature or both. The main parameter of the theory is the energy W0 of a kink on a step. Experimental data are consistent with a value of W0 between 0.2 and 0.3 eV, in agreement with very rough theoretical evaluations. Predictions are presented concerning the lineshape of diffraction spectra in the high-temperature rough phase, where intensities cannot be written as delta functions. The Bragg peak intensity vanishes just below the roughening transition temperature, TR, as exp(-constant*(TR-T)-12/), where the constant depends on the particular Bragg peak.

Source parameters from shallow events in the Rocky Mountain House earthquake swarm

We report here source parameters of the Rocky Mountain earthquake swarm derived from three-component digital data. During 6 days in October 1980, 21 events were recorded. Focal depths for these events are in the range of 1 ± 0.8 to 2 ± 2 km. Eleven events with local magnitudes from 2.1 to 2.8 yielded source parameters. Corner frequencies of the S-wave spectra were found in the range 6.2 ± 0.5 Hz, giving source dimensions of 160 ± 10 m. The corresponding P-wave corner frequencies are in the range 8.6 ± 3 Hz. The ratio of P to S corner frequencies varies from 0.9 to 2.1. There is a path effect between 13 and 16 Hz that could have affected these ratios. The average falloff over three components at high frequencies varies from −1.8 to −2.3. High stress drops, ranging from 47 to 263 bar (4.7–26.3 MPa), and apparent stresses, from 2.5 to 23 bar (0.25–2.3 MPa), were calculated. Five events have remarkably similar characteristics in the frequency and time domains. For these events the ratio of minimum strain energy W0, according to Kanamori, to the energy calculated using the integration scheme of Hanks and Thatcher was 3.7 ± 0.5. A theoretical value gives 3.1. The seismic efficiency ranges from 0.2 ± 0.04 to 0.17 ± 0.8. Large seismic moments for relatively small magnitudes were found. Some of these spectral characteristics are best explained as the result of displacement along a smooth fault.

Optical absorption in a heavily doped semiconductor with a narrow forbidden band

The coefficient of interband absorption in a heavily doped, strongly compensated semiconductor with a narrow forbidden band was calculated for emission frequencies ħω which are smaller than the widthɛg of the forbidden band. If the width of the forbidden band is smaller than the characteristic energy w0 of the random field produced by randomly distributed impurities, the optical absorption gap is missing and the coefficient of absorption increases with the frequency, with the increase being basically proportional toω.

Triple-Dipole Interaction. I. Theory

Third-order perturbation theory is applied to the van der waals-type interaction between neutral atoms. An interaction between triplets of atoms results. The derivation of the third-order energy interaction W0′′′, is outlined, the procedure being somewhat similar to that used by London in his application of second-order perturbation theory to interatomic interaction. Since the perturbing potential is limited to the dipole-dipole term, the energy W0′′′ is called the triple-dipole interaction. The latter depends not only on the interatomic distances but also on the shape of the triangle formed by the three atoms; W0′′′ is positive for all acute and negative for most obtuse triangles.