Journal Description
Physical Sciences Forum
Physical Sciences Forum
is an open access journal dedicated to publishing findings resulting from academic conferences, workshops and similar events in the area of physical sciences. Each conference proceeding can be individually indexed, is citable via a digital object identifier (DOI) and freely available under an open access license.
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Imprint Information
Open Access
ISSN: 2673-9984
Latest Articles
An Entropic Approach to Classical Density Functional Theory
Phys. Sci. Forum 2021, 3(1), 13; https://doi.org/10.3390/psf2021003013 - 24 Dec 2021
Abstract
The classical Density Functional Theory (DFT) is introduced as an application of entropic inference for inhomogeneous fluids in thermal equilibrium. It is shown that entropic inference reproduces the variational principle of DFT when information about the expected density of particles is imposed. This
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The classical Density Functional Theory (DFT) is introduced as an application of entropic inference for inhomogeneous fluids in thermal equilibrium. It is shown that entropic inference reproduces the variational principle of DFT when information about the expected density of particles is imposed. This process introduces a family of trial density-parametrized probability distributions and, consequently, a trial entropy from which the preferred one is found using the method of Maximum Entropy (MaxEnt). As an application, the DFT model for slowly varying density is provided, and its approximation scheme is discussed.
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Open AccessProceeding Paper
Quantum Mechanics as Hamilton–Killing Flows on a Statistical Manifold
Phys. Sci. Forum 2021, 3(1), 12; https://doi.org/10.3390/psf2021003012 - 21 Dec 2021
Abstract
The mathematical formalism of quantum mechanics is derived or “reconstructed” from more basic considerations of the probability theory and information geometry. The starting point is the recognition that probabilities are central to QM; the formalism of QM is derived as a particular kind
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The mathematical formalism of quantum mechanics is derived or “reconstructed” from more basic considerations of the probability theory and information geometry. The starting point is the recognition that probabilities are central to QM; the formalism of QM is derived as a particular kind of flow on a finite dimensional statistical manifold—a simplex. The cotangent bundle associated to the simplex has a natural symplectic structure and it inherits its own natural metric structure from the information geometry of the underlying simplex. We seek flows that preserve (in the sense of vanishing Lie derivatives) both the symplectic structure (a Hamilton flow) and the metric structure (a Killing flow). The result is a formalism in which the Fubini–Study metric, the linearity of the Schrödinger equation, the emergence of complex numbers, Hilbert spaces and the Born rule are derived rather than postulated.
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Open AccessProceeding Paper
Surrogate-Enhanced Parameter Inference for Function-Valued Models
Phys. Sci. Forum 2021, 3(1), 11; https://doi.org/10.3390/psf2021003011 - 21 Dec 2021
Abstract
We present an approach to enhance the performance and flexibility of the Bayesian inference of model parameters based on observations of the measured data. Going beyond the usual surrogate-enhanced Monte-Carlo or optimization methods that focus on a scalar loss, we place emphasis on
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We present an approach to enhance the performance and flexibility of the Bayesian inference of model parameters based on observations of the measured data. Going beyond the usual surrogate-enhanced Monte-Carlo or optimization methods that focus on a scalar loss, we place emphasis on a function-valued output of a formally infinite dimension. For this purpose, the surrogate models are built on a combination of linear dimensionality reduction in an adaptive basis of principal components and Gaussian process regression for the map between reduced feature spaces. Since the decoded surrogate provides the full model output rather than only the loss, it is re-usable for multiple calibration measurements as well as different loss metrics and, consequently, allows for flexible marginalization over such quantities and applications to Bayesian hierarchical models. We evaluate the method’s performance based on a case study of a toy model and a simple riverine diatom model for the Elbe river. As input data, this model uses six tunable scalar parameters as well as silica concentrations in the upper reach of the river together with the continuous time-series of temperature, radiation, and river discharge over a specific year. The output consists of continuous time-series data that are calibrated against corresponding measurements from the Geesthacht Weir station at the Elbe river. For this study, only two scalar inputs were considered together with a function-valued output and compared to an existing model calibration using direct simulation runs without a surrogate.
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Open AccessProceeding Paper
On Two Measure-Theoretic Aspects of the Full Bayesian Significance Test for Precise Bayesian Hypothesis Testing †
by
Phys. Sci. Forum 2021, 3(1), 10; https://doi.org/10.3390/psf2021003010 - 17 Dec 2021
Abstract
The Full Bayesian Significance Test (FBST) has been proposed as a convenient method to replace frequentist p-values for testing a precise hypothesis. Although the FBST enjoys various appealing properties, the purpose of this paper is to investigate two aspects of the FBST
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The Full Bayesian Significance Test (FBST) has been proposed as a convenient method to replace frequentist p-values for testing a precise hypothesis. Although the FBST enjoys various appealing properties, the purpose of this paper is to investigate two aspects of the FBST which are sometimes observed as measure-theoretic inconsistencies of the procedure and have not been discussed rigorously in the literature. First, the FBST uses the posterior density as a reference for judging the Bayesian statistical evidence against a precise hypothesis. However, under absolutely continuous prior distributions, the posterior density is defined only up to Lebesgue null sets which renders the reference criterion arbitrary. Second, the FBST statistical evidence seems to have no valid prior probability. It is shown that the former aspect can be circumvented by fixing a version of the posterior density before using the FBST, and the latter aspect is based on its measure-theoretic premises. An illustrative example demonstrates the two aspects and their solution. Together, the results in this paper show that both of the two aspects which are sometimes observed as measure-theoretic inconsistencies of the FBST are not tenable. The FBST thus provides a measure-theoretically coherent Bayesian alternative for testing a precise hypothesis.
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Open AccessProceeding Paper
The ABC of Physics
by
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Phys. Sci. Forum 2021, 3(1), 9; https://doi.org/10.3390/psf2021003009 - 10 Dec 2021
Abstract
Why quantum? Why spacetime? We find that the key idea underlying both is uncertainty. In a world lacking probes of unlimited delicacy, our knowledge of quantities is necessarily accompanied by uncertainty. Consequently, physics requires a calculus of number pairs and not only
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Why quantum? Why spacetime? We find that the key idea underlying both is uncertainty. In a world lacking probes of unlimited delicacy, our knowledge of quantities is necessarily accompanied by uncertainty. Consequently, physics requires a calculus of number pairs and not only scalars for quantity alone. Basic symmetries of shuffling and sequencing dictate that pairs obey ordinary component-wise addition, but they can have three different multiplication rules. We call those rules A, B and C. “A” shows that pairs behave as complex numbers, which is why quantum theory is complex. However, consistency with the ordinary scalar rules of probability shows that the fundamental object is not a particle on its Hilbert sphere but a stream represented by a Gaussian distribution. “B” is then applied to pairs of complex numbers (qubits) and produces the Pauli matrices for which its operation defines the space of four vectors. “C” then allows integration of what can then be recognised as energy-momentum into time and space. The picture is entirely consistent. Spacetime is a construct of quantum and not a container for it.
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Open AccessProceeding Paper
Statistical Mechanics of Unconfined Systems: Challenges and Lessons
Phys. Sci. Forum 2021, 3(1), 8; https://doi.org/10.3390/psf2021003008 - 09 Dec 2021
Abstract
Motivated by applications of statistical mechanics in which the system of interest is spatially unconfined, we present an exact solution to the maximum entropy problem for assigning a stationary probability distribution on the phase space of an unconfined ideal gas in an anti-de
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Motivated by applications of statistical mechanics in which the system of interest is spatially unconfined, we present an exact solution to the maximum entropy problem for assigning a stationary probability distribution on the phase space of an unconfined ideal gas in an anti-de Sitter background. Notwithstanding the gas’ freedom to move in an infinite volume, we establish necessary conditions for the stationary probability distribution solving a general maximum entropy problem to be normalizable and obtain the resulting probability for a particular choice of constraints. As a part of our analysis, we develop a novel method for identifying dynamical constraints based on local measurements. With no appeal to a priori information about globally defined conserved quantities, it is therefore applicable to a much wider range of problems.
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Open AccessProceeding Paper
Regularization of the Gravity Field Inversion Process with High-Dimensional Vector Autoregressive Models
by
and
Phys. Sci. Forum 2021, 3(1), 7; https://doi.org/10.3390/psf2021003007 - 07 Dec 2021
Abstract
Earth’s gravitational field provides invaluable insights into the changing nature of our planet. It reflects mass change caused by geophysical processes like continental hydrology, changes in the cryosphere or mass flux in the ocean. Satellite missions such as the NASA/DLR operated Gravity Recovery
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Earth’s gravitational field provides invaluable insights into the changing nature of our planet. It reflects mass change caused by geophysical processes like continental hydrology, changes in the cryosphere or mass flux in the ocean. Satellite missions such as the NASA/DLR operated Gravity Recovery and Climate Experiment (GRACE), and its successor GRACE Follow-On (GRACE-FO) continuously monitor these temporal variations of the gravitational attraction. In contrast to other satellite remote sensing datasets, gravity field recovery is based on geophysical inversion which requires a global, homogeneous data coverage. GRACE and GRACE-FO typically reach this global coverage after about 30 days, so short-lived events such as floods, which occur on time frames from hours to weeks, require additional information to be properly resolved. In this contribution we treat Earth’s gravitational field as a stationary random process and model its spatio-temporal correlations in the form of a vector autoregressive (VAR) model. The satellite measurements are combined with this prior information in a Kalman smoother framework to regularize the inversion process, which allows us to estimate daily, global gravity field snapshots. To derive the prior, we analyze geophysical model output which reflects the expected signal content and temporal evolution of the estimated gravity field solutions. The main challenges here are the high dimensionality of the process, with a state vector size in the order of to , and the limited amount of model output from which to estimate such a high-dimensional VAR model. We introduce geophysically motivated constraints in the VAR model estimation process to ensure a positive-definite covariance function.
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Open AccessProceeding Paper
Bayesian Surrogate Analysis and Uncertainty Propagation
Phys. Sci. Forum 2021, 3(1), 6; https://doi.org/10.3390/psf2021003006 - 13 Nov 2021
Cited by 1
Abstract
The quantification of uncertainties of computer simulations due to input parameter uncertainties is paramount to assess a model’s credibility. For computationally expensive simulations, this is often feasible only via surrogate models that are learned from a small set of simulation samples. The surrogate
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The quantification of uncertainties of computer simulations due to input parameter uncertainties is paramount to assess a model’s credibility. For computationally expensive simulations, this is often feasible only via surrogate models that are learned from a small set of simulation samples. The surrogate models are commonly chosen and deemed trustworthy based on heuristic measures, and substituted for the simulation in order to approximately propagate the simulation input uncertainties to the simulation output. In the process, the contribution of the uncertainties of the surrogate itself to the simulation output uncertainties is usually neglected. In this work, we specifically address the case of doubtful surrogate trustworthiness, i.e., non-negligible surrogate uncertainties. We find that Bayesian probability theory yields a natural measure of surrogate trustworthiness, and that surrogate uncertainties can easily be included in simulation output uncertainties. For a Gaussian likelihood for the simulation data, with unknown surrogate variance and given a generalized linear surrogate model, the resulting formulas reduce to simple matrix multiplications. The framework contains Polynomial Chaos Expansions as a special case, and is easily extended to Gaussian Process Regression. Additionally, we show a simple way to implicitly include spatio-temporal correlations. Lastly, we demonstrate a numerical example where surrogate uncertainties are in part negligible and in part non-negligible.
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Open AccessProceeding Paper
Orbit Classification and Sensitivity Analysis in Dynamical Systems Using Surrogate Models
Phys. Sci. Forum 2021, 3(1), 5; https://doi.org/10.3390/psf2021003005 - 05 Nov 2021
Abstract
Dynamics of many classical physics systems are described in terms of Hamilton’s equations. Commonly, initial conditions are only imperfectly known. The associated volume in phase space is preserved over time due to the symplecticity of the Hamiltonian flow. Here we study the propagation
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Dynamics of many classical physics systems are described in terms of Hamilton’s equations. Commonly, initial conditions are only imperfectly known. The associated volume in phase space is preserved over time due to the symplecticity of the Hamiltonian flow. Here we study the propagation of uncertain initial conditions through dynamical systems using symplectic surrogate models of Hamiltonian flow maps. This allows fast sensitivity analysis with respect to the distribution of initial conditions and an estimation of local Lyapunov exponents (LLE) that give insight into local predictability of a dynamical system. In Hamiltonian systems, LLEs permit a distinction between regular and chaotic orbits. Combined with Bayesian methods we provide a statistical analysis of local stability and sensitivity in phase space for Hamiltonian systems. The intended application is the early classification of regular and chaotic orbits of fusion alpha particles in stellarator reactors. The degree of stochastization during a given time period is used as an estimate for the probability that orbits of a specific region in phase space are lost at the plasma boundary. Thus, the approach offers a promising way to accelerate the computation of fusion alpha particle losses.
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Open AccessProceeding Paper
Survey Optimization via the Haphazard Intentional Sampling Method
Phys. Sci. Forum 2021, 3(1), 4; https://doi.org/10.3390/psf2021003004 - 05 Nov 2021
Abstract
In previously published articles, our research group has developed the Haphazard Intentional Sampling method and compared it to the Rerandomization method proposed by K.Morgan and D.Rubin. In this article, we compare both methods to the pure randomization method used for the Epicovid19 survey,
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In previously published articles, our research group has developed the Haphazard Intentional Sampling method and compared it to the Rerandomization method proposed by K.Morgan and D.Rubin. In this article, we compare both methods to the pure randomization method used for the Epicovid19 survey, conducted to estimate SARS-CoV-2 prevalence in 133 Brazilian Municipalities. We show that Haphazard intentional sampling can either substantially reduce operating costs to achieve the same estimation errors or, the other way around, substantially improve estimation precision using the same sample sizes.
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Open AccessProceeding Paper
Global Variance as a Utility Function in Bayesian Optimization
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Phys. Sci. Forum 2021, 3(1), 3; https://doi.org/10.3390/psf2021003003 - 05 Nov 2021
Abstract
A Gaussian-process surrogate model based on already acquired data is employed to approximate an unknown target surface. In order to optimally locate the next function evaluations in parameter space a whole variety of utility functions are at one’s disposal. However, good choice of
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A Gaussian-process surrogate model based on already acquired data is employed to approximate an unknown target surface. In order to optimally locate the next function evaluations in parameter space a whole variety of utility functions are at one’s disposal. However, good choice of a specific utility or a certain combination of them prepares the fastest way to determine a best surrogate surface or its extremum for lowest amount of additional data possible. In this paper, we propose to consider the global (integrated) variance as an utility function, i.e., to integrate the variance of the surrogate over a finite volume in parameter space. It turns out that this utility not only complements the tool set for fine tuning investigations in a region of interest but expedites the optimization procedure in toto.
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Open AccessProceeding Paper
A Weakly Informative Prior for Resonance Frequencies
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Phys. Sci. Forum 2021, 3(1), 2; https://doi.org/10.3390/psf2021003002 - 04 Nov 2021
Abstract
We derive a weakly informative prior for a set of ordered resonance frequencies from Jaynes’ principle of maximum entropy. The prior facilitates model selection problems in which both the number and the values of the resonance frequencies are unknown. It encodes a weakly
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We derive a weakly informative prior for a set of ordered resonance frequencies from Jaynes’ principle of maximum entropy. The prior facilitates model selection problems in which both the number and the values of the resonance frequencies are unknown. It encodes a weakly inductive bias, provides a reasonable density everywhere, is easily parametrizable, and is easy to sample. We hope that this prior can enable the use of robust evidence-based methods for a new class of problems, even in the presence of multiplets of arbitrary order.
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Open AccessProceeding Paper
Legendre Transformation and Information Geometry for the Maximum Entropy Theory of Ecology
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Phys. Sci. Forum 2021, 3(1), 1; https://doi.org/10.3390/psf2021003001 - 03 Nov 2021
Abstract
Here I investigate some mathematical aspects of the maximum entropy theory of ecology (METE). In particular I address the geometrical structure of METE endowed by information geometry. As novel results, the macrostate entropy is calculated analytically by the Legendre transformation of the log-normalizer
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Here I investigate some mathematical aspects of the maximum entropy theory of ecology (METE). In particular I address the geometrical structure of METE endowed by information geometry. As novel results, the macrostate entropy is calculated analytically by the Legendre transformation of the log-normalizer in METE. This result allows for the calculation of the metric terms in the information geometry arising from METE and, by consequence, the covariance matrix between METE variables.
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Open AccessAbstract
Nonperturbative QED on the Hopf Bundle
Phys. Sci. Forum 2021, 2(1), 43; https://doi.org/10.3390/ECU2021-09286 - 22 Jul 2021
Abstract
We consider the Dirac equation and Maxwell’s electrodynamics in spacetime, where a three-dimensional sphere is the Hopf bundle . The method of nonperturbative quantization of interacting Dirac and Maxwell fields is suggested. The corresponding
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We consider the Dirac equation and Maxwell’s electrodynamics in spacetime, where a three-dimensional sphere is the Hopf bundle . The method of nonperturbative quantization of interacting Dirac and Maxwell fields is suggested. The corresponding operator equations and the infinite set of the Schwinger–Dyson equations for Green’s functions is written down. To illustrate the suggested scheme of nonperturbative quantization, we write a simplified set of equations describing some physical situation. Additionally, we discuss the properties of quantum states and operators of interacting fields.
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Open AccessEditorial
A New MDPI Proceedings Journal: Physical Sciences Forum
Phys. Sci. Forum 2021, 1(1), 1; https://doi.org/10.3390/psf2021001001 - 25 Jun 2021
Abstract
Conferences and scientific events are an important part of scientific communication and offer researchers, from both academia and industry [...]
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Open AccessProceeding Paper
Gravity Variation Effects on the Growth of Maize Shoots
Phys. Sci. Forum 2021, 2(1), 21; https://doi.org/10.3390/ECU2021-10184 - 27 May 2021
Abstract
Gravity variation effects on plants provide definite changes. Normal Earth gravity (1G) and microgravity (µg) are possible variations for experimental purposes. On-board spaceflight microgravity experiments are rare and expensive, as the microgravity environment is an outstanding platform for research, application and education. A
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Gravity variation effects on plants provide definite changes. Normal Earth gravity (1G) and microgravity (µg) are possible variations for experimental purposes. On-board spaceflight microgravity experiments are rare and expensive, as the microgravity environment is an outstanding platform for research, application and education. A Clinostat was used for ground-based experiments to investigate the shoot morphology of maize plants at the Space Agency of Nigeria—National Space Research and Development Agency (NASRDA). A Clinostat device uses rotation to negate gravitational pull effects on plant growth and development. Maize was selected for this experiment because of its nutritional and economic importance, and its usability on the Clinostat. Plant shoot morphology is important for gravi-responses. Shoot curvature and shoot growth rate analyses were conducted on the shoots of a provitamin variety of maize. The seeds were planted into three Petri dishes (in parallel) in a wet chamber using a plant substrate—agar-agar. The experimental conditions were subject to relative humidity, temperature and light conditions. After 3 days of germination under 1G, two of the Petri dishes were left under 1G, serving as controls for shoot curvature and shoot growth rate analyses. The clinorotated sample was mounted on the Clinostat under: a fast rotation speed of 80 rpm, a horizontal rotation position and a clockwise rotation direction. The images of the samples were taken at a 30 min interval for 4 h. After observations, the shoot morphology of the seedlings was studied using ImageJ software. The grand average shoot angles and shoot lengths of all the seedlings were calculated following the experimental period to provide the shoot curvatures and shoot growth rates, respectively. The results show that the clinorotated sample had a reduced response to gravity, with 50.77°/h for the shoot curvature, while the 90°-turned sample had 55.49°/h. The shoot growth rate for the 1G sample was 1.25 cm/h, while that for the clinorotated sample was 1.26 cm/h. The clinorotated sample had an increased growth rate per hour compared to the counterpart 1G sample. These analytical results serve as preparation for future real-space experiments on maize and could be beneficial to the agriculture sector.
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Open AccessAbstract
Dynamics of Anisotropic Cylindrical Collapse in Energy-Momentum Squared Gravity
Phys. Sci. Forum 2021, 2(1), 40; https://doi.org/10.3390/ECU2021-09513 - 19 Mar 2021
Abstract
This paper deals with the dynamics of cylindrical collapse with anisotropic matter configuration in the context of energy-momentum squared gravity. This covariant generalization of general relativity allows the presence of T_abT^ab in the action of functional theory. Consequently, the relevant field equations are
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This paper deals with the dynamics of cylindrical collapse with anisotropic matter configuration in the context of energy-momentum squared gravity. This covariant generalization of general relativity allows the presence of T_abT^ab in the action of functional theory. Consequently, the relevant field equations are different from general relativity only in the presence of matter sources. In this theory, there is a maximum energy density and a minimum scale factor of the early universe. This means that there is a bounce at early times which avoids the presence of an early-time singularity. Moreover, this theory possesses a true sequence of cosmological eras. However, the cosmological constant does not play an important role in the early times and becomes important only after the matter-dominated era. In this theory, the “repulsive��? nature of the cosmological constant plays a crucial role at early times in resolving the singularity. We formulate the corresponding field equations as well as junction conditions. We construct dynamical equations through the Misner–Sharp technique and examine the impact of energy-momentum squared gravity on the collapse rate. We develop a relation among fluid parameters, correction terms and Weyl scalar and examine the effects of anisotropy, effective matter variables and correction terms on the collapsing phenomenon. Due to the presence of anisotropic pressure, spacetime is no longer considered to be conformally flat. To obtain conformally flat spacetime, we neglect the impact of anisotropy and assume the isotropic matter distribution which yields homogeneity of the energy density and conformally flat spacetime. The hydrodynamical force determines the stability of the system and prevents the collapsing as well as expanding process for the constant energy-momentum squared gravity model. We conclude that positive correction terms and anisotropy provide the anti-gravitational behavior leading to the stability of self-gravitating objects and hence prevent the collapsing process.
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Open AccessAbstract
The Cosmological Model Based on the Uncertainty-Mediated Dark Energy
by
Phys. Sci. Forum 2021, 2(1), 37; https://doi.org/10.3390/ECU2021-09515 - 19 Mar 2021
Abstract
The existence of the effective Lambda-term is a commonly accepted paradigm of modern cosmology, but the physical essence of this quantity remains absolutely unknown, and its numerical values are drastically different in the early and modern universe. In fact, the Lambda-term is usually
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The existence of the effective Lambda-term is a commonly accepted paradigm of modern cosmology, but the physical essence of this quantity remains absolutely unknown, and its numerical values are drastically different in the early and modern universe. In fact, the Lambda-term is usually introduced in the literature either by postulating arbitrary additional terms in the Lagrangians or by employing the empirical equations of state. In our recent series of papers (Yu.V. Dumin. Grav. and Cosmol., v.25, p.169 (2019); v.26, p. 259 (2020); v.27, in press (2021)), we tried to provide a more rigorous physical basis for the effective Lambda-term, starting from the time-energy uncertainty relation in the Mandelstam–Tamm form, which is appropriate for the long-term evolution of quantum systems. This results in the time-dependent Lambda-term, decaying as 1/t. The uncertainty-mediated cosmological model possesses a number of specific features, some of which look rather appealing: (1) While the standard cosmology involves a few very different stages (governed by the Lambda-term, radiation, dustlike matter, and again the Lambda-term), our model provides a universal description of the entire evolution of the universe by the same “quasi-exponential��? function. (2) As follows from the analysis of causal structure, the present-day cosmological horizon comprises a single domain developing from the Bing Bang. Therefore, the problems of the homogeneity and isotropy of matter, the absence of topological defects, etc. should be naturally resolved. (3) Besides, our model naturally explains the observed approximately flat 3D space, i.e., the solution with zero curvature is formed “dynamically��?, starting from the arbitrary initial conditions. (4) The age of the universe turns out to be much greater than in the standard cosmology; but this should not be a crucial drawback, because the most of problems are associated with insufficient rather than excessive age of the universe.
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Open AccessProceeding Paper
Second Order Glauber Correlation of Gravitational Waves Using the LIGO Observatories as Hanbury Brown and Twiss Detectors
by
and
Phys. Sci. Forum 2021, 2(1), 25; https://doi.org/10.3390/ECU2021-09519 - 19 Mar 2021
Abstract
The second order Glauber correlation of a simplified gravitational wave is investigated, using parameters from the first signal detected by LIGO. This simplified model spans the inspiral, merger, and ringdown phases of a black hole merger and was created to have a continuous
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The second order Glauber correlation of a simplified gravitational wave is investigated, using parameters from the first signal detected by LIGO. This simplified model spans the inspiral, merger, and ringdown phases of a black hole merger and was created to have a continuous amplitude, so there is no discontinuity between the phases. This allows for a trivial extraction of the intensity, which is necessary for determining the correlation between detectors. The two LIGO observatories can be used as detectors in a Hanbury Brown and Twiss interferometer for gravitational waves; these observatories measure the amplitude of the wave, so these measurements were used as the basis of the simplified model. The signal detected by the observatories is transient and is not consistent with chaotic or steady electromagnetic waves and thus the second order Glauber correlation function was calculated to produce physically meaningful results. To find correlations that are consistent with applications to electromagnetic waves, weighting functions for both models were studied in the integral equations for the Glauber correlation functions. The relationship between the transient and chaotic signals of both waveforms and their respective correlation functions was also examined. The second order Glauber correlation functions are a measure of intensity interference between independent detectors and has proven to be useful in both optics and particle physics. It has also been used in theoretical studies of primordial gravitational waves. The correlations can be used to define the degrees of coherence of a field, characterize multi-particle processes and assist in image enhancement.
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Open AccessAbstract
Can an Extra Dimension Pull Space-Time?
by
and
Phys. Sci. Forum 2021, 2(1), 4; https://doi.org/10.3390/ECU2021-09518 - 19 Mar 2021
Abstract
Over the years, efforts to unify gravity with other fundamental forces in nature has been an active field of research. Looking for the common origin of fundamental interactions, one may arrive at Kaluza–Klein type theories. Generalized Kaluza–Klein models offer an attractive possibility of
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Over the years, efforts to unify gravity with other fundamental forces in nature has been an active field of research. Looking for the common origin of fundamental interactions, one may arrive at Kaluza–Klein type theories. Generalized Kaluza–Klein models offer an attractive possibility of unifying gravity with the other fundamental forces aiming at the extension of space–time from 4D to higher “mathematical��? dimensions. In this paper, a generalization of the standard class of exact solutions in Kaluza–Klein (4 + 1) gravity are obtained for a homogeneous cosmological model filled with vacuum energy. In the algebraic and physical sense, these solutions generalize the previously found solutions in the literature. A unified and systematic treatment by solving the field equations in a straight forward manner is more appealing. The deceleration parameter shows that the model exhibits a transition from a decelerated to an accelerated universe. Recent observations have generated strong theoretical and observational evidence that the present expansion of the universe is in an accelerated phase. There is also observational evidence that beyond a certain value of redshift, the universe has been undergoing decelerated expansion. The models which describe transition from a decelerated to an accelerated phase are in the line of observational outcomes and of physical interest. The standard three-space expands indefinitely. Extra dimensions exhibit contraction as well as expansion with suitable values of the parameters. The model rejects the hypothesis of manifesting matter from extra dimensions. However, extra dimensions generate some attractive forces similar to gravity during the early evolution. Consequently, extra dimensions can be responsible for the past deceleration of the universe. The model seems to suggest an alternative mechanism pointing to a smooth transition from a decelerated phase to accelerated phase where the extra dimensions cause the transition.
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(This article belongs to the Proceedings of The 1st Electronic Conference on Universe)
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