Boundary Of Spacetime Research Articles

Counterterm method and thermodynamics of hairy black holes in a vector-tensor theory with Abelian gauge symmetry breaking

For a type of nonminimally coupled vector-tensor theories with Abelian gauge symmetry breaking in four-dimensional spacetime and correspondingly asymptotic non-AdS black hole solutions including a cosmological constant, we construct the appropriate boundary terms and derive the associated junction condition. In order to remove the divergences in the stress tensor which is localized on the spacetime boundary, we also involve the suitable surface counterterms into the total action. Using the counterterm method, we calculate the black hole mass. An implicit relation between the black hole carge $Q$ and other parameters is implied by combining the expression of the black hole mass with the first law of black hole thermodynamics. With this implicit relation, we can prove the inequality $Q\ensuremath{\le}M$ which is a general bound for most of charged black holes. Besides, the phase structure of black holes is also investigated in the grand canonical ensemble.

Recovery of time-dependent coefficients from boundary data for hyperbolic equations

We study uniqueness of the recovery of a time-dependent magnetic vector valued potential and an electric scalar-valued potential on a Riemannian manifold from the knowledge of the Dirichlet-to-Neumann map of a hyperbolic equation. The Cauchy data is observed on time-like parts of the space-time boundary and uniqueness is proved up to the natural gauge for the problem. The proof is based on Gaussian beams and inversion of the light ray transform on Lorentzian manifolds under the assumptions that the Lorentzian manifold is a product of a Riemannian manifold with a time interval and that the geodesic ray transform is invertible on the Riemannian manifold.

Complexity growth of massive black hole with a probe string

In this work, we study the computational complexity of massive gravity theory via the “Complexity = Action” conjecture. Our system contains a particle moving on the boundary of the black hole spacetime. It is dual to inserting a fundamental string in the bulk background. Then this string would contribute a Nambu–Goto term, such that the total action is composed of the Einstein–Hilbert term, Nambu–Goto term and the boundary term. We shall investigate the time development of this system, and mainly discuss the features of the Nambu–Goto term affected by the graviton mass and the horizon curvature in different dimensions. Our study could contribute interesting properties of complexity.

Особенности изображения хронотопа в повести А. И. Куприна «Колесо времени»

The purpose of the study is to determine features of depicting the chronotope of A. I. Kuprin’s novella “The Wheel of Time”, the main content of which is the Russian emigrant’s telling of his love story. Homesickness, traditional for the emigrant literature, fades into the background drowned out by the pain caused by downfall of a love affair and loss of the beloved. The study is novel in that it is the first to analyse in detail artistic space of the novella; to reconstruct the protagonist-narrator’s biography, whose life fits into historical time and correlates with the author’s image. As a result, it is found that space-time boundaries of the novella expand in the story told by the main character; the historical chronotope becomes the background, the biographical one is outlined, the event chronotope is the central one.

Summing over geometries in string theory

We examine the question how string theory achieves a sum over bulk geometries with fixed asymptotic boundary conditions. We discuss this problem with the help of the tensionless string on {mathrm{mathcal{M}}}_3times {mathrm{S}}^3times {mathbbm{T}}^4 (with one unit of NS-NS flux) that was recently understood to be dual to the symmetric orbifold SymN ( {mathbbm{T}}^4 ). We strengthen the analysis of [1] and show that the perturbative string partition function around a fixed bulk background already includes a sum over semi-classical geometries and large stringy corrections can be interpreted as various semi-classical geometries. We argue in particular that the string partition function on a Euclidean wormhole geometry factorizes completely into factors associated to the two boundaries of spacetime. Central to this is the remarkable property of the moduli space integral of string theory to localize on covering spaces of the conformal boundary of ℳ3. We also emphasize the fact that string perturbation theory computes the grand canonical partition function of the family of theories ⊕N SymN ( {mathbbm{T}}^4 ). The boundary partition function is naturally expressed as a sum over winding worldsheets, each of which we interpret as a ‘stringy geometry’. We argue that the semi-classical bulk geometry can be understood as a condensate of such stringy geometries. We also briefly discuss the effect of ensemble averaging over the Narain moduli space of {mathbbm{T}}^4 and of deforming away from the orbifold by the marginal deformation.

Modeling Transient Flows in Heterogeneous Layered Porous Media Using the Space–Time Trefftz Method

In this study, we developed a novel boundary-type meshless approach for dealing with two-dimensional transient flows in heterogeneous layered porous media. The novelty of the proposed method is that we derived the Trefftz space–time basis function for the two-dimensional diffusion equation in layered porous media in the space–time domain. The continuity conditions at the interface of the subdomains were satisfied in terms of the domain decomposition method. Numerical solutions were approximated based on the superposition principle utilizing the space–time basis functions of the governing equation. Using the space–time collocation scheme, the numerical solutions of the problem were solved with boundary and initial data assigned on the space–time boundaries, which combined spatial and temporal discretizations in the space–time manifold. Accordingly, the transient flows through the heterogeneous layered porous media in the space–time domain could be solved without using a time-marching scheme. Numerical examples and a convergence analysis were carried out to validate the accuracy and the stability of the method. The results illustrate that an excellent agreement with the analytical solution was obtained. Additionally, the proposed method was relatively simple because we only needed to deal with the boundary data, even for the problems in the heterogeneous layered porous media. Finally, when compared with the conventional time-marching scheme, highly accurate solutions were obtained and the error accumulation from the time-marching scheme was avoided.

Energetic boundary element method for accurate solution of damped waves hard scattering problems

The paper deals with the numerical solution of 2D wave propagation exterior problems including viscous and material damping coefficients and equipped by Neumann boundary condition, hence modeling the hard scattering of damped waves. The differential problem, which includes, besides diffusion, advection and reaction terms, is written as a space–time boundary integral equation (BIE) whose kernel is given by the hypersingular fundamental solution of the 2D damped waves operator. The resulting BIE is solved by a modified Energetic Boundary Element Method, where a suitable kernel treatment is introduced for the evaluation of the discretization linear system matrix entries represented by space–time quadruple integrals with hypersingular kernel in space variables. A wide variety of numerical results, obtained varying both damping coefficients and discretization parameters, is presented and shows accuracy and stability of the proposed technique, confirming what was theoretically proved for the simpler undamped case. Post-processing phase is also taken into account, giving the approximate solution of the exterior differential problem involving damped waves propagation around disconnected obstacles and bounded domains.

Producing (extra)ordinary death on the farm: unruly encounters and contaminated calves

ABSTRACT In 2010, twenty-eight bovines on a Pennsylvania beef farm were exposed to a hydraulic fracturing wastewater leak on their grazing pasture. Over the following year, eleven out of seventeen calves born to the exposed animals died. The farmers framed the deaths as outside normal deathly production on the farm, while state institutions claimed the deaths resulted from the farmers’ negligence, framing them as ordinary. I draw on necropolitics to examine how death becomes a normalized mode of capital production in agri-food systems, investigating how the wastewater spill and calves’ deaths ruptured the everyday production of bovine death. The paper argues that death must occur in prescribed sites and at approved times to function as a site of value accumulation in capitalist agriculture. I examine how the spill and calf death events emerged through promiscuous entanglements between overlapping modes of capital extraction across and through the site of the farm. Using assemblages, I trace unruly, promiscuous encounters at this food-energy contact zone to consider how the calves’ deaths render visible the space-time boundaries used to manage more-than-human mortality as a metabolic process in livestock production, and highlight disparate power relations between diverse necropolitical actors and modes of governance.

No inner-horizon theorem for black holes with charged scalar hairs

We establish a no inner-horizon theorem for black holes with charged scalar hairs. Considering a general gravitational theory with a charged scalar field, we prove that there exists no inner Cauchy horizon for both spherical and planar black holes with non-trivial scalar hair. The hairy black holes approach to a spacelike singularity at late interior time. This result is independent of the form of scalar potentials as well as the asymptotic boundary of spacetimes. We prove that the geometry near the singularity takes a universal Kasner form when the kinetic term of the scalar hair dominates, while novel behaviors different from the Kasner form are uncovered when the scalar potential become important to the background. For the hyperbolic horizon case, we show that hairy black hole can only has at most one inner horizon, and a concrete example with an inner horizon is presented. All these features are also valid for the Einstein gravity coupled with neutral scalars.

Discipline and distinction in the age of the Internet: a sociological study of the fitness practice

This article examines popular fitness sports and home fitness software in China. Drawing on Michel Foucault’s theory of discipline, Norbert Elias’ study on civilization, and Jean Baudrillard’s study on the consumer society, the authors reveal the formation of a new body discipline mechanism against the background of the Internet society and the consumer society. On the one hand, the external disciplinary strategies have been upgraded, including the spatial strategy of liquidity and visibility, the linear and rhythmic time strategy, and the knowledge strategy. On the other hand, different from Foucault’s discussion of discipline, we introduce positive self-discipline. As a unique consumption practice, fitness practices promote a new form of self-discipline among practitioners who also pursue distinctive social positions. The core content of the self-discipline strategy includes code manipulation, time consumption, moral display, and self-writing. In addition, with the continuous infiltration of Internet technologies in daily life, the space-time boundaries of physical discipline gradually blur, whereas the micro-distribution of power changes into a daily distribution form.

Vacuum polarization on topological black holes with Robin boundary conditions

We compute the renormalized vacuum polarization for a massless, conformally coupled scalar field on asymptotically anti-de Sitter black hole backgrounds. Mixed (Robin) boundary conditions are applied on the spacetime boundary. We consider black holes with nonspherical event horizon topology as well as spherical event horizons. The quantum scalar field is in the Hartle-Hawking state, and we employ Euclidean methods to calculate the renormalized expectation values. Far from the black hole, we find that the vacuum polarization approaches a finite limit, which is the same for all boundary conditions except Dirichlet boundary conditions.

BMS algebras in 4 and 3 dimensions, their quantum deformations and duals

BMS symmetry is a symmetry of asymptotically flat spacetimes in vicinity of the null boundary of spacetime and it is expected to play a fundamental role in physics. It is interesting therefore to investigate the structures and properties of quantum deformations of these symmetries, which are expected to shed some light on symmetries of quantum spacetime. In this paper we discuss the structure of the algebra of extended BMS symmetries in 3 and 4 spacetime dimensions, realizing that these algebras contain an infinite number of distinct Poincaré subalgebras, a fact that has previously been noted in the 3 dimensional case only. Then we use these subalgebras to construct an infinite number of different Hopf algebras being quantum deformations of the BMS algebras. We also discuss different types of twist-deformations and the dual Hopf algebras, which could be interpreted as noncommutative, extended quantum spacetimes.

Determination of a Wave Field in a Laterally Inhomogeneous Medium from Boundary Data

The Cauchy problem is studied for a perturbed wave equation in a half-plane with data given on a part of the space-time boundary. The equation in consideration describes a wave process in a laterally inhomogeneous medium. A reconstruction algorithm is proposed, which is applicable to the problem of determining a nonstationary wave field from boundary data arising in geophysics.

Игроизация пространственно-временного бытия человека в контексте виртуальной реальности

The article considers the spatial and temporal changes manifested in the virtual form of gamification of existence. The definition of the virtual form of gamification of existence is given. On the basis of included observation, the spatial and temporal transformations of socio-cultural reality are rethought, and the philosophical-anthropological approach makes it possible to establish the dependence of the strategies of individual and group behaviour on the inclusion of game actions in the virtual existence. The analysis of the virtual form of gamification of existence as an event and as a co-being is given. The virtual form of gamification of existence is supported by artificially created events, presented as serious incidents, replaced by new ones for tomorrow. The transformation of the structure of free time is considered, which allows transferring most of the life of a contemporary into leisure. The spatial and temporal model of the virtual form of gamification of human existence visually and mentally dissolves the contemporary in the virtual gaming environment. A contemporary, acting out the events, appears in the form of bricolage, multiple images demonstrating strategies of both personal and group behavior. In the virtual interface, time becomes human-sized, allowing in others to see themselves. The space-time boundaries of the virtual form of gamification of existence negate the authenticity of real life, replacing and displacing it with experimental simulation that forms dependence.

TITLE AS A FIGURATIVE AND SYMBOLIC CENTER OF BORIS PASTERNAK’S POETRY COLLECTION “OVER THE BARRIERS”

This article, based on my report at the international conference dedicated to the 130th anniversary of B. L. Pasternak (China, Hangzhou, Zhejiang University, 8-10 November 2020), is aimed at studying the nature of the relationship between the title of the collection and the texts of the poems included in it. The relevance of the work is determined by the anthropocentric orientation of modern linguistics, which focuses on the linguistic personality and the world picture of the creative individual. The theoretical section discusses the methodological foundations of the research, reveals conceptual categories, highlights a complex of factors that affect the perception and understanding of Pasternak’s lyrics. The practical part of this article contains the results of a contextual analysis of the lyric works titles. The symbolic meanings of the title-trope are presented, the associative features of which correlate with the idea of overcoming limitations in the broad sense of the word. In poetic texts, the referent of the key sign is manifested by lexemes: body (intimate space), courtyard (home space), sleep (border space), street and canals (segments of urban space), railway (technogenic space), weather conditions (obstacles in the perception of the environment), ice (natural shackles that are temporary) etc. The conclusions are formulated in the following judgments: 1) the title, which is considered to be global and local “ad hoc” connectivity, makes the entire collection complete, strengthens its internal unity due to the motive of overcoming space-time boundaries; 2) the formula “over the barriers” symbolizes the boundaries both in personal and biographical terms and in the philosophical and psychological sense, emphasizes the complexity and significance of the poet’s creative quests.

Chronotope in Uzbek novels of the period of independence

The article examines the problem of creative development of national-literary traditions, in particular the literary and artistic heritage of Navoi, which significantly expanded the space-time boundaries of national novels of the period of independence.The boundaries of space and time of the national novels of the independence period are expanding. There is no doubt that the same phenomenon observed in the literary process is a positive sign for the national novel.

Quantum field theory on global anti-de Sitter space-time with Robin boundary conditions

We compute the vacuum polarization for a massless, conformally coupled scalar field on the covering space of global, four-dimensional, anti-de Sitter space-time. Since anti-de Sitter space is not globally hyperbolic, boundary conditions must be applied to the scalar field. We consider general Robin (mixed) boundary conditions for which the classical evolution of the field is well-defined and stable. The vacuum expectation value of the square of the field is not constant unless either Dirichlet or Neumann boundary conditions are applied. We also compute the thermal expectation value of the square of the field. For Dirichlet boundary conditions, both thermal and vacuum expectation values approach the same well-known limit on the space-time boundary. For all other Robin boundary conditions (including Neumann boundary conditions), the vacuum and thermal expectation values have the same limit on the space-time boundary, but this limit does not equal that in the Dirichlet case.

Solving Transient Groundwater Inverse Problems Using Space–Time Collocation Trefftz Method

This paper presents a space–time meshfree method for solving transient inverse problems in subsurface flow. Based on the transient groundwater equation, we derived the Trefftz basis functions utilizing the method of separation of variables. Due to the basis functions completely satisfying the equation to be solved, collocation points are placed on the space–time boundaries. Numerical solutions are approximated based on the superposition theorem. Accordingly, the initial and boundary conditions are both regarded as space–time boundary conditions. Forward and inverse examples are conducted to validate the proposed approach. Emphasis is placed on the two-dimensional boundary detection problem in which the nonlinearity is solved using the fictitious time integration method. Results demonstrate that approximations with high accuracy are acquired in which the boundary data on the absent boundary may be efficiently recovered even when inaccessible partial data are provided.

The decay of space-time to the eternal parallel historical epochs, time entanglement and time machine

The article shows how mathematics can describe the process of the decay of space-time to infinite number of different space-times, which from the point of view of some observer are eternal. The relation of this decay to the time entanglement of quantum fields on an infinitely distant boundary of space-time within the 𝐴𝑑𝑆/𝐶𝐹 𝑇-correspondence is considered.

Electromagnetic field correlators and the Casimir effect for planar boundaries in AdS spacetime with application in braneworlds

We evaluate the correlators for the vector potential and for the field strength tensor of the electromagnetic field in the geometry of two parallel planar plates in AdS spacetime. Two types of boundary conditions are considered on the plates. The first one is a generalization of perfect conductor boundary condition and the second one corresponds to the confining boundary conditions. By using the expressions for the correlators, the vacuum expectation values (VEVs) of the photon condensate and of the electric and magnetic fields squared are investigated. As another important local characteristic of the vacuum state we consider the VEV of the energy-momentum tensor. The Casimir forces acting on the plates are decomposed into the self-action and interaction parts. It is shown that the interaction forces are attractive for both types of boundary conditions. At separations between the plates larger than the curvature radius of the background geometry they decay exponentially as functions of the proper distance. The self-action force per unit surface of a single plate does not depend on its location and depending on the boundary condition and on the number of spatial dimensions can be either attractive or repulsive with respect to the AdS boundary. By using the generalized zeta function technique we also evaluate the total Casimir energy. Applications are given in $Z_{2}$-symmetric braneworld models of the Randall-Sundrum type for vector fields with even and odd parities.