Isomiddin Nishonov, Javlon Rayimbaev, Saeed Ullah Khan
et al.
Abstract Testing dark matter effects on gravity around black holes in the framework of gravity theories through observational data is an essential task of relativistic astrophysical studies. In this work, we first obtain a new spacetime solution for a black hole surrounded by perfect fluid dark matter (PFDM) in modified gravity (MOG). The MOG field is assumed to be a gravitational vector field. We investigate the vector fields with combined effects of PFDM on spacetime properties: event horizon radius, scalar invariants such as the Ricci scalar, the square of the Ricci tensor, and Kretchman scalars. We investigate the circular motion of test particles in the spacetime of the black hole, taking into account the MOG field interaction on the particle geodesics. The energy and angular momentum of the particles corresponding to circular orbits are studied. In addition, we explore how the PFDM and MOG fields change the position of innermost stable circular orbits (ISCOs) and their corresponding energy and angular momentum values. Moreover, we study the energy efficiency rate around the black hole in the Novikov and Thorns thin accretion disc model. We analyze collisional cases of the particles near the black hole and study the effects of the fields on the critical angular momentum in which particles can collide near the black hole and the center-of-mass energy of the colliding particles.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Asalkhon Alimova, Farruh Atamurotov, Ahmadjon Abdujabbarov
et al.
Abstract The motion of spinning particles around a quantum-corrected black hole is examined in this paper. We investigate the dynamics of spinning test particles by using the Mathisson–Papapetrou–Dixon equations, the Tulczyjew spin-supplementary condition, and restricting the motion to the equatorial plane. We determine the innermost stable circular orbit (ISCO), effective potential, and effective force and examine how these depend on the black hole’s $$\alpha $$ α parameter and the particle’s s spin. However, we also take into account a superluminal bound on the motion of the spinning particle since its kinematical four-velocity and dynamical four-momentum are not always parallel. We also show how the parameter $$\alpha $$ α affects the maximum value of the spin parameter s. We determine the critical angular momentum of the particle for which a collision is possible by investigating collisions of spinning particles close to the horizon of a black hole. Finally, we compute the particle’s center-of-mass energy $$\mathcal {E}_{cm}$$ E cm and analyze how the spin of the colliding particles affects it.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Mukesh Kumar Singh, Shasvath J. Kapadia, Aditya Vijaykumar
et al.
Templates modeling just the dominant mode of gravitational radiation are generally sufficient for the unbiased parameter inference of near-equal-mass compact binary mergers. However, neglecting the subdominant modes can bias the inference if the binary is significantly asymmetric, very massive, or has misaligned spins. In this work, we explore if neglecting these subdominant modes in the parameter estimation of nonspinning binary black hole mergers can bias the inference of their population-level properties such as mass and merger redshift distributions. Assuming the design sensitivity of the advanced LIGO-Virgo detector network, we find that neglecting subdominant modes will not cause a significant bias in the population inference, although including them will provide more precise estimates. This is primarily because asymmetric binaries are expected to be rarer in our detected sample, due to their intrinsic rareness and the observational selection effects. The increased precision in the measurement of the maximum black hole mass can help in better constraining the upper mass gap in the mass spectrum.
In this article, a graph-theoretic method (taking advantage of constraints among sets associated with the corresponding parity-check matrices) is applied for the construction of a double low-density parity-check (D-LDPC) code (also known as LDPC code pair) in a joint source-channel coding (JSCC) system. Specifically, we pre-set the girth of the parity-check matrix for the LDPC code pair when jointly designing the two LDPC codes, which are constructed by following the set constraints. The constructed parity-check matrices for channel codes comprise an identity submatrix and an additional submatrix, whose column weights can be pre-set to be any positive integer numbers. Simulation results illustrate that the constructed D-LDPC codes exhibit significant performance improvement and enhanced flexible frame length (i.e., adaptability under various channel conditions) compared with the benchmark code pair.
Manuel Tuniz, Armando Consiglio, Denny Puntel
et al.
Abstract Long-range electronic ordering descending from a metallic parent state constitutes a rich playground to study the interplay of structural and electronic degrees of freedom. In this framework, kagome metals are in the most interesting regime where both phonon and electronically mediated couplings are significant. Several of these systems undergo a charge density wave transition. However, to date, the origin and the main driving force behind this charge order is elusive. Here, we use the kagome metal ScV6Sn6 as a platform to investigate this problem, since it features both a kagome-derived nested Fermi surface and van-Hove singularities near the Fermi level, and a charge-ordered phase that strongly affects its physical properties. By combining time-resolved reflectivity, first principles calculations and photo-emission experiments, we identify the structural degrees of freedom to play a fundamental role in the stabilization of charge order, indicating that ScV6Sn6 features an instance of charge order predominantly originating from phonons.
Materials of engineering and construction. Mechanics of materials
Abstract Interactions of hard partons in the Quark Gluon Plasma (QGP) created with relativistic heavy ion collisions lead to characteristic modifications of the internal structure of reconstructed jets. A large part of the observed jet sub-structure modifications stem from the QGP’s response to energy and momentum deposited by hard partons. Good control over medium response in theoretical calculations is thus instrumental to a quantitative understanding of medium modified (quenched) jets in heavy ion collisions. We present an improved way of handling the medium response in the jet quenching model Jewel and present results for a variety of jet sub-structure observables. The new recoil handling is more versatile and robust than the old scheme, giving a better control over many observables and, in particular, greatly improves the description of the jet mass.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Suraci Stefano S., Oliveira Leonardo C., Klein Ivandro
et al.
The most common approaches for assigning weights to observations in minimum L1-norm (ML1) is to introduce weights of p or p\sqrt{p}, p being the weights vector of observations given by the inverse of variances. Hence, they do not take covariances into consideration, being appropriated only to independent observations. To work around this limitation, methods for decorrelation/unit-weight reduction of observations originally developed in the context of least squares (LS) have been applied for ML1, although this adaptation still requires further investigations. In this article, we presented a deeper investigation into the mentioned adaptation and proposed the new ML1 expressions that introduce weights for both independent and correlated observations; and compared their results with the usual approaches that ignore covariances. Experiments were performed in a leveling network geometry by means of Monte Carlo simulations considering three different scenarios: independent observations, observations with “weak” correlations, and observations with “strong” correlations. The main conclusions are: (1) in ML1 adjustment of independent observations, adaptation of LS techniques introduces weights proportional to p\sqrt{p} (but not p); (2) proposed formulations allowed covariances to influence parameters estimation, which is unfeasible with usual ML1 formulations; (3) introducing weighs of p provided the closest ML1 parameters estimation compared to that of LS in networks free of outliers; (4) weighs of p\sqrt{p} provided the highest successful rate in outlier identification with ML1. Conclusions (3) and (4) imply that introducing covariances in ML1 may adversely affect its performance in these two practical applications.
Naotaka Yoshikawa, Kazuma Ogawa, Yoshua Hirai
et al.
Weyl semimetals exhibit a unique feature known as Weyl nodes, which give rise to non-trivial topological features such as an anomalous Hall effect, and there are many efforts to try and control such properties. Here, the authors report light-induced chirality switching in a ferromagnetic Weyl semimetal Co3Sn2S2 using circularly polarized mid-infrared light pulse excitation.
The concept of representativeness is the main distinguishing characteristic of specialised corpora in comparison to other sets of texts. The Coruña Corpus of English Scientific Writing currently comprises four published subcorpora (astronomy, life sciences, history, and philosophy) plus three others under compilation (physics, chemistry and linguistics). In this paper we aim to assess the lexical density of the text samples in CETA, the Corpus of English Texts on Astronomy, by means of the ReCor tool, a posteriori. The study is motivated by the following question: does quantitative representativeness analysis using ReCor provide, in the form of a cross-check, further validation of previous research on the representativeness of CETA? Previous work (Crespo and Moskowich, 2010) has indicated that the CETA corpus is well designed and valid for the purposes for which it was intended. We will here suggest metrics to measure these findings. The most important contribution of this study is to offer quantitative data collection results using the ReCor tool, which allows data triangulation and consequently ensures overall data quality. Results show that data analysis with the ReCor tool supports previous findings, and thus we are able to verify that CETA is indeed representative of the language of its time and register.
Matteo Fraschini, Simone Maurizio La Cava, Luca Didaci
et al.
The idea of estimating the statistical interdependence among (interacting) brain regions has motivated numerous researchers to investigate how the resulting connectivity patterns and networks may organize themselves under any conceivable scenario. Even though this idea has developed beyond its initial stages, its practical application is still far away from being widespread. One concurrent cause may be related to the proliferation of different approaches that aim to catch the underlying statistical interdependence among the (interacting) units. This issue has probably contributed to hindering comparisons among different studies. Not only do all these approaches go under the same name (functional connectivity), but they have often been tested and validated using different methods, therefore, making it difficult to understand to what extent they are similar or not. In this study, we aim to compare a set of different approaches commonly used to estimate the functional connectivity on a public EEG dataset representing a possible realistic scenario. As expected, our results show that source-level EEG connectivity estimates and the derived network measures, even though pointing to the same direction, may display substantial dependency on the (often arbitrary) choice of the selected connectivity metric and thresholding approach. In our opinion, the observed variability reflects the ambiguity and concern that should always be discussed when reporting findings based on any connectivity metric.
We present a room temperature Graphene Quantum Dots (GQDs) based optical gas sensor for carbon dioxide gas detection. GQDs were prepared by a hydrothermal method and deposited on a quartz substrate using a drop-casting technique. The size of synthesized GQDs is in the range of 10 to 20 nm. GQDs films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), photoluminescence (PL) and UV-Vis absorption spectroscopy. The gas sensing measurements were studied using optical absorbance changes of GQDs film upon exposure to different concentrations of CO _2 gas. The as-prepared gas sensor showed a significant sensitivity with a partially reversible response to CO _2 gas, indicating its great potential to pave a way toward a novel CO _2 gas sensor.
Materials of engineering and construction. Mechanics of materials, Chemical technology
Andrea Murari, Michele Lungaroni, Emmanuele Peluso
et al.
Understanding the details of the correlation between time series is an essential step on the route to assessing the causal relation between systems. Traditional statistical indicators, such as the Pearson correlation coefficient and the mutual information, have some significant limitations. More recently, transfer entropy has been proposed as a powerful tool to understand the flow of information between signals. In this paper, the comparative advantages of transfer entropy, for determining the time horizon of causal influence, are illustrated with the help of synthetic data. The technique has been specifically revised for the analysis of synchronization experiments. The investigation of experimental data from thermonuclear plasma diagnostics proves the potential and limitations of the developed approach.
Abstract We consider a generalization of the two-dimensional Liouville conformal field theory to any number of even dimensions. The theories consist of a log-correlated scalar field with a background Q $$ \mathcal{Q} $$-curvature charge and an exponential Liouville-type potential. The theories are non-unitary and conformally invariant. They localize semiclassically on solutions that describe manifolds with a constant negative Q $$ \mathcal{Q} $$-curvature. We show that C T is independent of the Q $$ \mathcal{Q} $$-curvature charge and is the same as that of a higher derivative scalar theory. We calculate the A-type Euler conformal anomaly of these theories. We study the correlation functions, derive an integral expression for them and calculate the three-point functions of light primary operators. The result is a higher-dimensional generalization of the two-dimensional DOZZ formula for the three-point function of such operators.
Nuclear and particle physics. Atomic energy. Radioactivity
Vikram S. Vijayaraghavan, Ryan G. James, James P. Crutchfield
Collective organization in matter plays a significant role in its expressed physical properties. Typically, it is detected via an order parameter, appropriately defined for each given system’s observed emergent patterns. Recent developments in information theory, however, suggest quantifying collective organization in a system- and phenomenon-agnostic way: decomposing the system’s thermodynamic entropy density into a localized entropy, that is solely contained in the dynamics at a single location, and a bound entropy, that is stored in space as domains, clusters, excitations, or other emergent structures. As a concrete demonstration, we compute this decomposition and related quantities explicitly for the nearest-neighbor Ising model on the 1D chain, on the Bethe lattice with coordination number k = 3 , and on the 2D square lattice, illustrating its generality and the functional insights it gives near and away from phase transitions. In particular, we consider the roles that different spin motifs play (in cluster bulk, cluster edges, and the like) and how these affect the dependencies between spins.
J. Javier Brey, Vicente Buzón, Maria Isabel García de Soria
et al.
The dynamics of a system of hard spheres enclosed between two parallel plates separated a distance smaller than two particle diameters is described at the level of kinetic theory. The interest focuses on the behavior of the quasi-two-dimensional fluid seen when looking at the system from above or below. In the first part, a collisional model for the effective two-dimensional dynamics is analyzed. Although it is able to describe quite well the homogeneous evolution observed in the experiments, it is shown that it fails to predict the existence of non-equilibrium phase transitions, and in particular, the bimodal regime exhibited by the real system. A critical revision analysis of the model is presented , and as a starting point to get a more accurate description, the Boltzmann equation for the quasi-two-dimensional gas has been derived. In the elastic case, the solutions of the equation verify an H-theorem implying a monotonic tendency to a non-uniform steady state. As an example of application of the kinetic equation, here the evolution equations for the vertical and horizontal temperatures of the system are derived in the homogeneous approximation, and the results compared with molecular dynamics simulation results.
C. J. Merchant, S. Matthiesen, N. A. Rayner
et al.
Surface temperature is a key aspect of weather and climate, but the term may
refer to different quantities that play interconnected roles and are observed
by different means. In a community-based activity in June 2012, the EarthTemp
Network brought together 55 researchers from five continents to improve the
interaction between scientific communities who focus on surface temperature
in particular domains, to exploit the strengths of different observing
systems and to better meet the needs of different communities. The workshop
identified key needs for progress towards meeting scientific and societal
requirements for surface temperature understanding and information, which are
presented in this community paper. A "whole-Earth" perspective is required
with more integrated, collaborative approaches to observing and understanding
Earth's various surface temperatures. It is necessary to build understanding
of the relationships between different surface temperatures, where presently
inadequate, and undertake large-scale systematic intercomparisons. Datasets
need to be easier to obtain and exploit for a wide constituency of users,
with the differences and complementarities communicated in readily understood
terms, and realistic and consistent uncertainty information provided. Steps
were also recommended to curate and make available data that are presently
inaccessible, develop new observing systems and build capacities to
accelerate progress in the accuracy and usability of surface temperature
datasets.