Problem Of Gravity Research Articles

The Hadamard condition on a Cauchy surface and the renormalized stress-energy tensor

Given a Cauchy surface in a curved spacetime and a suitably defined quantum state on the CCR algebra of the Klein-Gordon quantum field on that surface, we show, by expanding the squared spacetime geodesic distance and the 'U' and 'V' Hadamard coefficients (and suitable derivatives thereof) in sufficiently accurate covariant Taylor expansions on the surface that the renormalized expectation value of the quantum stress-energy tensor on the surface is determined by the geometry of the surface and the first 4 time derivatives of the metric off the surface, in addition to the Cauchy data for the field's two-point function. This result has been anticipated in and is motivated by a previous investigation by the authors on the initial value problem in semiclassical gravity, for which the geometric initial data corresponds, a priori, to the spatial metric on the surface and up to 3 time derivatives off the surface, but where it was argued that the fourth derivative can be obtained with aid of the field equations on the initial surface.

A Quantization for the Toy Model of Black Hole and a Suggestion to the Unification Theory

In my previous paper about the correlations between quantum mechanics and the four different natural forces, I suggested that there may be a fifth force or even the existence of a new particle. However, it remains a mystery to physicists, even after nearly a hundred years, that they cannot unify these four natural forces. This may be because there are indeed too many variables for them to consider. Also, there is a possibility that quantum mechanics may coexist with quantum field theory. In the present paper, this author proposes that there may be a misconception in the computational equation for relative time or gaps in the system for measuring time between quantum mechanics and general relativity. Hence, one may still not be able to unify these natural forces. This author suggests that we may need to rewrite parts of quantum mechanics – the Schrödinger equation – or even the general relativity equation. Additionally, this author proposes that there may be a bridge equation converting between quantum mechanics and general relativity. Moreover, this author has employed the non-trivial zeta zeros to simulate the black hole or the so-called black hole toy model. In practice, there may be an electromagnetic field surrounding the boundary of the black hole, as well as the existence of a continuum along the boundary contour. This author hopes that, in such a case, we may decode those high-frequency electromagnetic waves into useful information and take a further step toward verifying Stephen Hawking’s famous theory on black hole radiation and information entropy. In fact, this author has used the HKLam statistical model theory to express the electromagnetic field energy-stress tensor (with the possibility of quantization) to analogically establish a quantized model for the Einstein Gravitational Field Equation. Hence, the problem of quantum gravity may then be solved. Last but not least, this author also expects that humanity may finally find a way to unify quantum mechanics and general relativity through modifications to the current quantum gravity theory, such as my proposed bridge-converting equation, etc.

Quantum Field Theory of Black Hole Perturbations with Backreaction: I General Framework

In a seminal work, Hawking showed that natural states for free quantum matter fields on classical spacetimes that solve the spherically symmetric vacuum Einstein equations are KMS states of non-vanishing temperature. Although Hawking’s calculation does not include the backreaction of matter on geometry, it is more than plausible that the corresponding Hawking radiation leads to black hole evaporation which is, in principle, observable. Obviously, an improvement of Hawking’s calculation including backreaction is a problem of quantum gravity. Since no commonly accepted quantum field theory of general relativity is available yet, it has been difficult to reliably derive the backreaction effect. An obvious approach is to use the black hole perturbation theory of a Schwarzschild black hole of fixed mass and to quantize those perturbations. However, it is not clear how to reconcile perturbation theory with gauge invariance beyond linear perturbations. In recent work, we proposed a new approach to this problem that applies when the physical situation has an approximate symmetry, such as homogeneity (cosmology), spherical symmetry (Schwarzschild), or axial symmetry (Kerr). The idea, which is surprisingly feasible, is to first construct the non-perturbative physical (reduced) Hamiltonian of the reduced phase space of fully gauge invariant observables and only then apply perturbation theory directly in terms of observables. The task to construct observables is then disentangled from perturbation theory, thus allowing to unambiguously develop perturbation theory to arbitrary orders. In this first paper of the series we outline and showcase this approach for spherical symmetry and second order in the perturbations for Einstein–Klein–Gordon–Maxwell theory. Details and generalizations to other matter and symmetry and higher orders will appear in subsequent companion papers.

Constructing all BPS black hole microstates from the gravitational path integral

Understanding how to prepare and count black hole micro-states by using the gravitational path integral is one of the most important problems in quantum gravity. Nevertheless, a state-by-state count of black hole microstates is difficult because the apparent number of degrees of freedom available in the gravitational effective theory can vastly exceed the entropy of the black hole, even in the special case of BPS black holes. In this paper, we show that we can use the gravitational path integral to prepare a basis for the Hilbert space of all BPS black hole microstates. We find that the dimension of this Hilbert space computed by an explicit state count is in complete agreement with the degeneracy obtained from the Gibbons-Hawking prescription. Specifically, this match includes all non-perturbative corrections in 1/GN. Such corrections are, in turn, necessary in order for this degeneracy of BPS states to match the non-perturbative terms in the 1/GN expansion in the string theory count of such microstates.

High-volume utilization of circulating fluidized bed fly ash for the production of autoclaved aerated concrete: Performance optimization and hydration characteristics

Circulating fluidized bed fly ash (CFA) is a waste emitted from coal combustion process in circulating fluidized bed boilers. The high SO3 and f-CaO content severely limits its application in building materials. The purpose of this study is to explore the possibility of large-scale application of CFA in autoclaved aerated concrete (AAC). The preparation parameters of AAC were discussed and the performance was optimized. Moreover, the workability and environmental properties of AAC were explored. The results indicated that AAC was well adapted to high CFA content, although a high CFA content caused a higher water demand as well as a reduction in the silicon content. The introduction of quartz sand and blast furnace slag effectively addressed the problems of insufficient active silica and high specific gravity. When the CFA doping was 50 %, H4 sample showed the best mechanical properties (3.82 MPa and 641 kg/m3), which meet the requests of A3.5, B06 in the Chinese national standard GB/T 11968–2020. Moreover, the toxicity leaching results showed that H4 sample was green and harmless. During the performance optimization process, more well-crystallized tobermorite was produced, whose crystal form changed from acicular to slat. Massive C-S-H gels and better crystallinity of tobermorite were observed, where were bonded and intercalated with each other, thus enhancing the properties. The paper may provide guidance for high dosing of CFA in AAC.

The Computational Universe: Quantum Quirks and Everyday Reality, Actual Time, Free Will, the Classical Limit Problem in Quantum Loop Gravity and Causal Dynamical Triangulation

The Computational Universe: Quantum Quirks and Everyday Reality, Actual Time, Free Will, the Classical Limit Problem in Quantum Loop Gravity and Causal Dynamical Triangulation

A Quantization for the Toy Model of Black Hole and a Suggestion to the Unification Theory

In my previous paper about the correlations about the quantum mechanics between four different natural forces, I have suggested that there may be a fifth force or even the existence of a new particle. However, it may be still a mysterious that physicists for nearly hundreds of years that they cannot unify these four natural forces. This may be because there are indeed too many variables for them considerate. Also there is a twin such that the quantum machanics may coexist with the quantum field theory. In the present paper, this author proposes that there may be a misconcept in the computational equation for our relative time or the gaps in the system of measure time between quantum mechanics and general relativity. Hence, one may still cannot unify these natural forces. This author suggests that we need to rewrite parts of our QM – the Schrödinger Equation or even the GR equation. Besides, this author also proposes there may be a bridge converting equation for the quantum mechanics and the general relativity. Moreover, this author has employed the non-trivial zeta zeros to stimulate the black hole or the so-called black hole toy model. In practice, there may be an electromagnetic field laying around the boundary of the black hole as well as the existing of a continumm in the such boundary contour. This author hopes that in such case, we may decode back those high frequency electromagnetic waves into the useful information and may go a further step to have a verification for the famous Stephen Hawking’s theory between the black hole radition and the information entropy. In fact, this author has used the HKLam statistical model theory to express the electromagnetic field energy-stress tensor (with the possibility of quantization) to analogically establish a quantized model for the Einstein Gravitational Field Equation. Hence, the problem of the quantum gravity may then be solved. Last but not least, this author may also expect that we – human may finally find a way to unify the quantum mechanics and the general relativity through the modification to the present quantum gravity theory from my suggested bridge converting equation etc.

Extremely compact sources (ECS): a new potential field filtering method

We present a new filtering method for potential fields, based on modelling the fields in terms of very compact solutions, i.e., the sources are expected to occupy the smallest allowable volume in the source domain. The selected solutions, which we call “Extremely Compact Sources” (ECS) form a sort of atomized model, which still satisfies the non-unique inverse problem of gravity and magnetic fields. The ECS model is not only characterized by sparsity, but also by large values of the physical property (density or magnetic susceptibility). The sparse nature of the model allows for the definition of a highly localized filter, which can be obtained by simply specifying the atoms to be selected in a given area. This feature allows managing tasks normally impossible with traditional filters, such as the separation of interfering anomalies having a similar wavenumber content. In addition, the procedure can perform a very effective regional/residual separation. We demonstrate the method on synthetic cases and apply it in the real case of gravity data of Campi Flegrei volcanic area (Italy), where we use the ECS filtering to isolate the gravity effect of the Mount Olibano dome.

Holographic study on Einstein ring for a charged black hole in conformal gravity

Under the help of AdS/CFT correspondence, the Einstein ring of a charged black hole in conformal gravity has been studied. As an alternative to standard Einstein’s theory, the conformal gravity is both renormalizable and unitary. And such conformal theory can naturally solve some troublesome problems in physics, such as the quantum gravity problem, the dark matter problem and so on. Considering the conformal gravity has many advantages, therefore in this paper, we study Einstein ring and the effect of gravity-related parameters c0, temperature T and chemical potential u on such Einstein ring in the conformal gravity through the holographic method. Explicitly, imposing an oscillating Gauss source on one side of the AdS boundary which propagates in the bulk, the response functions are derived on the other side of the boundary. Given the proposed wave optics system, the Einstein rings are observed as expected. All these results reveal that when the observer locates at the north pole, there always exists the Einstein ring and surrounding concentric stripes. And such ring becomes into a luminosity-deformed ring or light spot while the observer departs away from the north pole. We also investigate the effect of temperature T, chemical potential u and gravity-related parameters c0 on the ring radius. We find the ring radius increases with the decrease of the temperature, increase of the chemical potential, and increase of the gravity-related parameters respectively. And more, in conformal gravity, because the charge does not appear in the metric but is given by the constraint relation, the chemical potential affects the radius of the ring differently compared with that in Einstein’s gravity. To check the results in the framework of holography, we investigate the ingoing angle of photon at the photon ring via geometric optics and find it is consistent with the angle of Einstein ring obtained via holography.

(223) Specific Training Needs of Student Midwives in Sexual Health and Clinical Sexology

Abstract Introduction According to the WHO, sexuality is an integral part of human life, encompassing all dimensions of human beings: physical, emotional, mental, and social well-being associated with sexuality, involving a positive and respectful approach. It is essential to educate and train health professionals such as midwives to address sexual problems and provide the necessary information to their clients, in order to ensure comprehensive and quality care. There is still a lack of specific sexual health training programs in the midwifery curriculum in several countries worldwide. Objective This study aims to assess the student midwives’ training needs in sexual health and clinical sexology. Methods It is a knowledge, attitudes, and practices cross-sectional online study that took place over 5 weeks starting March 1st, 2023. All enrolled student midwives in public and private midwifery schools in the country were contacted through the schools’ social media groups. The online questionnaire was a 29-item Google form elaborated in concertation with the Frequency, Gravity Problem (FGP) grid of questions. Results The study included 206 student midwives (answer rate: 87%). The participants were representative of the population of student midwives (31% 1st, 33% 2nd, and 36% 3rd year and 31% from the North, 38% from the center, and 31% from the South of the country). The participants’ mean age was 22,1± 1,04 years and 96% were single. When asked about their experience with sexual interviews, 60.7% felt uncomfortable. The reasons for that feeling were the absence of previous learning simulations and experiences (84%), the lack of confidence in their knowledge (70%), the fear of a potential lack of interest of the clients about sexual health (59%), sexuality is taboo (28%). Regarding their training and education in sexual health and clinical sexology, 94% declared that it was only theoretical, 47% considered it as unorganized and 68,5% thought that there was a lack of correlation between the time allowed and the content of the sessions. The instructors were judged as qualified by 36% of the participants. The resources were considered useful by 19%. And 23.3% of the students enrolled in other non-academic training in sexology during the previous year. The expressed need for specific sexology training was expressed in 94%. The needs were regarding knowledge in 55%, Attitudes in 80%, and practices in 55%. Conclusions A specific academic curriculum in sexual health and clinical sexology is a necessity within the student midwives' training. This educational program needs to reinforce some knowledge and practices and mainly address the attitudes of healthcare professionals toward clients asking for information and/or help regarding their sexual health. Prevention has also to be integrated into this program. Role-playing and simulations in small groups seem the most adapted pedagogical techniques to re-enforce attitudes within students. Disclosure No.

(052) Sexual Health and Clinical Sexology Specific Training Needs of Residents in Gynecology and Obstetrics

Abstract Introduction Assuming that the Obstetrician and Gynecologist (ObGyn) is the natural and first interlocutor for sexual questions in women, particular attention should be paid to their specific training in sexual health and clinical sexology. However, it turns out that the latter is neglected with little attention given to the development or implementation of specific curricular programs within the gynecologists’ residency programs. Objective This study aims to: - Identify and analyze the specific needs of the ObGyn residents in terms of education and training in Sexual Health and Clinical Sexology. - Discuss the methods of integrating a specific sexology training into their residency program to be adapted to the needs thus identified. Methods It is a knowledge, attitudes, and practices cross-sectional online study that took place over 5 weeks starting May 1st, 2021. All the ObGyn residents registered at the National College of Gynecology and Obstetrics were contacted through the College’s social media groups. The online questionnaire was a 9-item Google form elaborated in concertation with the Frequency, Gravity Problem (FGP) grid leading to 33 questions. Results With a response rate of 34 %, 94 residents participated in the survey. The participants were representative of the local population of ObGyn residents with an equal proportion of participants from the 5 years of the program. According to 69% of the participants, complaints or sexual disorders are rarely encountered during the ObGyn residency program courses. This finding was not correlated with the participants' residency level (R= 0.258, p> 0.05). The most frequently encountered sexual disorders during the clinical consultations were sexual disorders with pain (44.68%) and in particular vaginismus (75%). Regardless of the frequency of the disorders, the difficulties reported were primarily in the domain of knowledge (67.5%); then in the domain of know-how or practices (68%), and often in the domain of interpersonal skills (42.2%). Following the application of the rating system of the FGP grid, the main problems identified concerned sexual disorders with pain, in particular, vaginismus and then a decrease in female desire. Conclusions Following the analysis of these results and a review of the literature, we were able to propose the outline of a project to implement basic academic education and training in clinical sexology for the ObGyn residents. Disclosure No.

The chaotic four-body problem in Newtonian gravity – II. An ansatz-based approach to analytical solutions

ABSTRACT In this paper, we continue our analysis of the chaotic four-body problem and our study of binary–binary interactions in star clusters. We present a general ansatz-based analytical treatment using statistical mechanics, where each outcome of the four-body problem is regarded as some variation of the three-body problem. For example, when two single stars are produced (the 2 + 1 + 1 outcome), each ejection event is modelled as its own three-body interaction by assuming that the ejections are well separated in time. This is a generalization of the approach adopted in Paper I, based on the density-of-states formalism. There are three possible outcomes for the four-body problem with negative total energies: 2 + 2, 2 + 1 + 1, and 3 + 1. For each outcome, we apply an ansatz-based approach to deriving analytical distribution functions that describe the properties of the products of chaotic four-body interactions involving point particles. To test our theoretical distributions, we perform a set of scattering simulations in the equal-mass point-particle limit using FEWBODY, where we vary the initial ratio of binary semimajor axes. We compare our final theoretical distributions to the simulations for each particular scenario, finding consistently good agreement between the two. The highlights of our results include that binary–binary scatterings act to systematically destroy binaries producing instead a binary and two ejected stars (when the initial binary semimajor axes are similar) or a stable triple (when the initial semimajor axes are very different). The 2 + 2 outcome produces the widest binaries, and the 2 + 1 + 1 outcome produces the most compact binaries.

Primitive and gravity modulation of periodical heat transfer along magnetic-driven porous cone with thermal conductivity and surface heat flux

The significant goal of present problem is to evaluate oscillating frequency and amplitude in heat and magnetic flux with thermal conductivity and heat flux effects across magnetized porous cone under lower gravitational region. To maintain heat transport efficiency, the thermal conductivity of conducting fluid is assumed as temperature dependent. The magnetic-driven cone is placed in lower gravitational region. To improve the heating rate across the magnetic-driven porous cone, the convective heating conditions are applied. The implications of thermal conductivity, surface heat flux, and reduced gravity on the periodic behavior of convective heat transfer characteristics of conducting fluid across porous gravity-driven cone is the novelty of this research. Using the appropriate non-dimensional variables, the model's nonlinear governing partial differential has been converted into a dimensionless form. The proposed model is solved later with the help of finite difference approach. The dimensionless form of the equations is reduced to the convenient form for numerical algorithm. The influence of adjusting parameters, such as thermal conductivity parameter ζ, reduced gravity parameter Rg, Biot number Bi, Prandtl number Pr, mixed convection parameter λ, porosity parameter Ω, magnetic prandtl number γ and some others stationary parameters has been highlighted. By using FORTRAN tool, the numerical outcomes are explored in graphs and tabular form. It is depicted that magnetic field enhances as Biot number decreases because magnetic field insulates the excessive heating across the magnetic-driven porous cone. It is noticed that significant amplitude in fluid velocity is noticed with prominent changes as reduced gravity increases. It is concluded that fluctuations in heat transport increases as parameter γ decreases under thermal conductivity because magnetic material insulates the extreme heat across the porous cone. The recent thermal conductivity and lowered gravity problem is significant in the fields of radioactive waste, cooling electronic components, storing nuclear, catalysts, heat exchangers, the underground storage of radioactive or nonnuclear materials, aircrafts and space vehicles.

Fast large-scale gravity modeling using a high-order compact cascadic multigrid strategy

A new high-order compact (HOC) cascadic multigrid (MG) strategy is developed for modeling large-scale complex gravity problems on nonuniform rectilinear grids. First, the governing 3D Poisson’s gravitational potential equation is discretized by a novel HOC difference scheme, which allows for Robin boundary conditions to further reduce the computational domain. Then, the resulting asymmetric linear system of equations is solved by a generalized extrapolation cascadic MG (gEXCMG) method augmented with a novel MG prolongation operator. The quartic interpolation and completed Richardson extrapolation assist this MG prolongation operator to produce a good initial guess for the biconjugate gradient stabilized smoother. Two synthetic and SEG/EAGE salt models are examined to verify the presented approach. Results indicate that our algorithm can efficiently and accurately produce the gravity signals for complex geologic models. Moreover, the comparisons with the state-of-the-art algebraic MG solvers demonstrate that our gEXCMG solver offers substantially better efficiency with significantly less memory consumption. Therefore, our newly developed method has the potential for serving as a forward engine in large-scale gravity inversions.

Towards AdS distances in string theory

The AdS Distance Conjecture proposes to assign a notion of distance between AdS vacua in quantum gravity. We perform some initial developments of this idea. We first propose more sharply how to define a metric on conformal variations of AdS through the action. This metric is negative, making the distance ill-defined, a property relating to the famous conformal factor problem of quantum gravity. However, in string theory, variations of the AdS conformal factor are accompanied by variations of the internal dimensions and of the background flux. We propose an action metric, which accounts for all of these variations simultaneously. Accounting for the variations of the overall volume of the internal dimensions can flip the sign of the action metric making it positive. This positivity is related to the absence of scale separation between the internal and external dimensions: the negative external conformal contribution must be sub-dominant to the positive internal contribution. We then focus specifically on the families of solutions of eleven-dimensional supergravity on AdS4 × S7 and AdS7 × S4. For these, there is only a single further additional contribution to the action metric coming from variations of the Freund-Rubin flux. This contribution is subtle to implement, and the unique prescription we find requires singling out the radial direction of AdS as special. Adding the flux contribution yields an overall total action metric which becomes positive for both the AdS4 and AdS7 families of solutions. The final result is therefore a procedure which yields a well-defined distance for these families of solutions.

Quaternion Quantum Mechanics II: Resolving the Problems of Gravity and Imaginary Numbers

We present a quaternion representation of quantum mechanics that allows its ontological interpretation. The correspondence between classical and quaternion quantum equations permits one to consider the universe (vacuum) as an ideal elastic solid. Elementary particles would have to be standing or soliton-like waves. Tension induced by the compression and twisting of the elastic medium would increase energy density, and as a result, generate gravity forcing and affect the wave speed. Consequently, gravity could be described by an index of refraction.

On the ghost problem of conformal gravity

We study the metric perturbations around the de Sitter and Minkowski backgrounds in Conformal Gravity. We confirm the presence of ghosts in both cases. In the de Sitter case, by applying the Maldacena boundary conditions — the Neumann boundary condition and the positive-frequency mode condition — to the metric, we show that one cannot recover a general solution for the perturbations. In turn, alongside the Neumann boundary condition, we derive an additional condition with which the perturbations of conformal gravity and dS perturbations of Einstein gravity with cosmological constant coincide. We further show that the Neumann boundary condition does not lead to a general solution in Minkowski space. Conversely, we derive the alternative boundary conditions, with which we attain an agreement between the perturbations of conformal and Einstein gravity in full generality, thus removing the ghost of conformal gravity.

Triple interference, non-linear Talbot effect and gravitization of the quantum

Recently we have discussed a new approach to the problem of quantum gravity in which the quantum mechanical structures that are traditionally fixed, such as the Fubini–Study metric in the Hilbert space of states, become dynamical and so implement the idea of gravitizing the quantum. In this paper we elaborate on a specific test of this new approach to quantum gravity using triple interference in a varying gravitational field. Our discussion is driven by a profound analogy with recent triple-path interference experiments performed in the context of non-linear optics. We emphasize that the triple interference experiment in a varying gravitational field would deeply influence the present understanding of the kinematics of quantum gravity and quantum gravity phenomenology. We also discuss the non-linear Talbot effect as another striking phenomenological probe of gravitization of the geometry of quantum theory.

A NEW COMBINED TECHNIQUE FOR SOLVING NONLINEAR GRAVITY PROBLEMS FROM PLANETARY TOPOGRAPHY, GRAVITY FIELD DATA AND CRUSTAL THICKNESS WITH THE USE OF THROWING OFF ALGORITHM

We test a new combined technique of solving nonlinear gravity problems using three types of datasets: gravity field, topography and crustal thickness in the Elysium Planitia region on Mars.

Note on the action with the Schwarzian at the stretched horizon

In this paper, we discuss the quantization of an interesting model of Carlip which appeared recently. It shows a way to associate boundary degrees of freedom to the stretched horizon of a stationary non-extremal black hole, as has been done in JT gravity for near-extremal black holes. The path integral now contains an integral over the boundary degrees of freedom, which are time reparametrizations of the stretched horizon keeping its length fixed. These boundary degrees of freedom can be viewed as elements of $Diff(S^1)/S^1$, which is the coadjoint orbit of an ordinary coadjoint vector under the action of the Virasoro group. From the symplectic form on this manifold, we obtain the measure in the boundary path integral. Doing a one-loop computation about the classical solution, we find that the one-loop answer is not finite, signalling that either the classical solution is unstable or there is an indefiniteness problem with this action, similar to the conformal mode problem in quantum gravity. Upon analytically continuing the field, the boundary partition function we get is independent of the inverse temperature and does not contribute to the thermodynamics at least at one-loop. This is in contrast to the study of near-extremal black holes in JT gravity, where the entire contribution to thermodynamics is from boundary degrees of freedom.