Search

© 1991 The American Physical Society. We are very grateful to Jorma Louko for many useful conversations. L.G. and G.M. would like to thank Massachusetts Institute of Technology (MIT), where most of this work was done, for warm hospitality during their visit. L.G. and G.M. were supported by the Spanish Ministerio de Educacion y Ciencia. J.J.H. was supported in part by funds provided by the U.S. Department of Energy (DOE) under Contract No. DE-aCO2-76ER03069., We study a class of minisuperspace models consisting of a homogenous isotropic universe with a minimally coupled homogenous scalar field with a potential alpha cosh(2-phi) + beta sinh(2-phi), where alpha and beta are arbitrary parameters. This includes the case of a pure exponential potential exp(2-phi), which arises in the dimensional reduction to four dimensions of five-dimensional Kaluza-Klein theory. We study the classical Lorentzian solutions for the model and find that they exhibit exponential or power-law inflation. We show that the Wheeler-DeWitt equation for this model is exactly soluble. Concentrating on the two particular cases of potentials cosh(2-phi) and exp(2-phi), we consider the Euclidean minisuperspace path integral for a propagation amplitude between fixed scale factors and scalar-field configurations. In the gauge N = 0 (where N is the rescaled lapse function), the path integral reduces, after some essentially trivial functional integrations, to a single nontrivial ordinary integral over N. Because the Euclidean action is unbounded from below, N must be integrated along a complex contour for convergence. We find all possible complex contours which lead to solutions of the Wheeler-DeWitt equation or Green's functions of the Wheeler-DeWitt operator, and we give an approximate evaluation of the integral along these contours, using the method of steepest descents. The steepest-descent contours may be dominated by saddle points corresponding to exact solutions to the full Einstein-scalar equations which may be real Euclidean, real Lorentzian, or complex. We elucidate the conditions under which each of these different types of solution arise. For the exp(2-phi) potential, we evaluate the path integral exactly. Although we cannot evaluate the path integral in closed form for the cosh(2-phi) potential, we show that for particular N contours the amplitude may be written as a given superposition of exact solutions to the Wheeler-DeWitt equation. By choosin, U.S. Department of Energy (DOE), Spanish Ministerio de Educacion y Ciencia, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 1996 The American Physical Society. We are very grateful to Mariano Moles for helpful discussions and support. C.B. was supported by a Spanish Ministry of Education and Science (MEC) grant. L.J.G. was supported by the MEC and the British Council. P.G.-D. acknowledges DGICYT for financial support under Research Projects Nos. PB94-0107 and PB93-0139. G.A.M.M. was supported by funds provided by DGICYT and MEC under Contract Adjunct to the Project No. PB93-0139., Starting with a procedure for dealing with general asymptotic behavior, we construct a quantum theory for asymptotically anti-de Sitter wormholes. We follow both the path integral formalism and the algebraic quantization program proposed by Ashtekar. By adding suitable surface terms, the Euclidean action of the asymptoically anti-de Sitter wormholes can be seen to be finite and gauge invariant. This action determines an appropriate variational problem for wormholes. We also obtain the wormhole wave functions of the gravitational model and show that all the physical states of the quantum theory are superpositions of wormhole states., Spanish Ministry of Education and Science, British Council, DGICYT (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 1999 The American Physical Society. We thank C. Barceló, C. Cabrillo, P.F. González-Díaz, G.A. Mena Marugán, and M.A. alle Basagoiti for discussions. J.M.R. is also grateful to J.M. Quintana. We had support from the University of the Basque Country (Project No. UPV 063.310-EB225/95) from Junta de Andalucía, and from DGICYT (Spain) under Project Nos. PB94-0107 and PB93- 0139., We characterize good clocks, which are naturally subject to fluctuations, in statistical terms. We also obtain the master equation that governs the evolution of quantum systems according to these clacks and find its general solution. This master equation is diffusive and produces loss of coherence, Moreover, real clocks can he described in terms of effective interactions that are nonlocal in time. Alternatively, they can be modeled by an effective thermal bath coupled to the system. [S1050-2947(99)04905-7]., University of the Basque Country, Junta de Andalucía, DGICYT (Spain), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© World Scientific Publ Co Pte Ltd I am very grateful to Jonathan Halliwell and Max Bañados for fruitful discussions and suggestions and for a critical reading of the manuscript. I also thank Alex Mikovi´c and Roya Mohayaee for useful conversations. The author was supported by a joint fellowship from the Ministerio de Educación y Ciencia (Spain) and the British Council., The existence of a fundamental scale, a lower bound to any output of a position measurement, seems to be a model-independent feature of quantum gravity. In fact, different approaches to this theory lead to this result. The key ingredients for the appearance of this minimum length are quantum mechanics, special relativity and general relativity. As a consequence, classical notions such as causality or distance between events cannot be expected to be applicable at this scale. They must be replaced by some other, yet unknown, structure., Ministerio de Educación y Ciencia (Spain), British Council., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

In this dissertation I will explore the question whether various entities commonly used in quantum field theory can be “constructed". In particular, can spacetime be “constructed" out of building blocks, and can Berezin integral be “constructed" in terms of Riemann integrals. As far as “constructing" spacetime out of building blocks, it has been attempted by multiple scientific communities and various models were proposed. But the common downfall is they break the principles of relativity. I will explore the ways of doing so in such a way that principles of relativity are respected. One of my approaches is to replace points with some entities that have a direction. In one of the sections, those entities are tangent vectors, in the other section they are pairs of points. In both cases, the success of respecting relativity is partial. On the one hand, I successfully removed preferred time axis. But, on the other hand, I still did not restore the symmetry under Lorentz group (or some modification of Lorentz group). For this reason, I also explored a different approach where I designed a matrix model for spacetime. In this case, I successfully restored Eucledian symmetry. Restoring the MInkowksian symmetry proved to be iii more difficult, and, depending on the models, came with the price. In both cases, though, the qestion of whether the resulting quantum field theory approximates the one that we know is left as an open question. There are reasons to hope that it does, but rigorously finding out whether that is the case is left for the future research. As far as constructing Berezin integral in terms of Riemann integrals, this was not attempted nearly as much (although there was one attempt in 1983 by Rabin, and possibly a couple of other isolated attempts). I have attempted to address it in my joint paper with Thomas Scanlon where we supplemented the anticommutting wedge product with Clifford algebra. This essentially amounts to “geometric algebra" mod

This course runs parallel to 8.02, but assumes that students have some knowledge of vector calculus. The class introduces Maxwell's equations, in both differential and integral form, along with electrostatic and magnetic vector potential, and the properties of dielectrics and magnetic materials. This class was taught by an undergraduate in the Experimental Study Group (ESG). Student instructors are paired with ESG faculty members, who advise and oversee the students' teaching efforts.

We generalize the exact predictive regularity of symmetry groups to give an algebraic theory of patterns, building from a core principle of future equivalence. For topological patterns in fully-discrete one-dimensional systems, future equivalence uniquely specifies a minimal semiautomaton. We demonstrate how the latter and its semigroup algebra generalizes translation symmetry to partial and hidden symmetries. This generalization is not as straightforward as previously considered. Here, though, we clarify the underlying challenges. A stochastic form of future equivalence, known as predictive equivalence, captures distinct statistical patterns supported on topological patterns. Finally, we show how local versions of future equivalence can be used to capture patterns in spacetime. As common when moving to higher dimensions, there is not a unique local approach, and we detail two local representations that capture different aspects of spacetime patterns. A previously developed local spacetime variant of future equivalence captures patterns as generalized symmetries in higher dimensions, but we show that this representation is not a faithful generator of its spacetime patterns. This motivates us to introduce a local representation that is a faithful generator, but we demonstrate that it no longer captures generalized spacetime symmetries. Taken altogether, building on future equivalence, the theory defines and quantifies patterns present in a wide range of classical field theories.

Black holes are one of the most interesting objects in the universe, and studying these objects should give exciting results. This research will investigate the General Theory of Relativity, explaining the essence of the theory needed for deriving solutions for a Schwarzschild black hole. This knowledge leads to deriving the equations of motion of a bosonic scalar field around a Schwarzschild black hole. Computing the dynamical evolution of that scalar field, and taking the limit far away from the black hole, gives an approximation derivation of the Schrödinger equation. This study opens many doors to future research about black holes and scalar fields., Svarta hål är ett av de mest intressanta objekten i universum, och därför, att studera dessa föremål bör ge spännande resultat.I detta arbete kommer den allmänna relativitetsteorin att studeras och förklaras med allt som behövs för att härledalösningar för en Schwarzschild svart hål. Denna kunskap leder till att härleda rörelseekvationerna för ett bosoniskt skalärfält runt ett Schwarzschild svart hål.Genom att beräkna den dynamiska utvecklingen av det skalära fältet och ta gränsen långt bort från svarta hålet,så kommer det at ge en approximativ härledning av Schrödinger ekvationen. Den här typen av studier öppnar många dörrar för framtida forskning om svarta hål och skalära fält.

In this dissertation, we investigate how some properties of quantum mechanics integrate in our description of the geometry of spacetime. This is done both at a theoretical and phenomenological level. In the first chapter, we give a brief introduction to the development of quantum mechanical ideas in our current understanding of spacetime and gravity. In particular, we motivate the necessity of a holographic description of gravity, as well as review some of the essential properties of the AdS/CFT correspondence.In the second chapter, we use this holographic duality to ask how the geometry of a particular bulk system is encoded in a non-gravitational field theory. In particular, we review and use the light-cone cuts prescription, which has been proposed as a method to reconstruct the conformal metric of a holographic spacetime. With this framework, we explore how additional information about the bulk geometry gets encoded in the structure of these light-cone cuts. We pay special attention on how the hyperbolic angle related to a cusp in the light-cone cut encodes information about the matter content of the spacetime. We provide an explicit numerical example reconstructing the metric for a four-dimensional spacetime composed by the superposition of a boson star and a gas of radiation in AdS.The full bulk path integral in a Lorentzian formulation of holography includes metrics that violate boundary causality. This leads to the following puzzle: The commutator of two field theory operators at spacelike-separated points on the boundary must vanish. However, if these points are causally related in a bulk metric, then the bulk calculation of the commutator will be nonzero. It would appear that the integral over all metrics of this commutator must vanish exactly for holography to hold. This is puzzling since it must also be true if the commutator is multiplied by any other operator. Upon a careful treatment of boundary conditions in holography, in the third chapter of this t

The modeling of black holes is an important desideratum for any quantum theory of gravity. Not only is a classical black hole metric sought, but also agreement with the laws of black hole thermodynamics. In this paper, we describe how these goals are achieved in string theory. We review black hole thermodynamics, and then explicate the general stringy derivation of classical spacetimes, the construction of a simple black hole solution, and the derivation of its entropy. With that in hand, we address some important philosophical and conceptual questions: the confirmatory value of the derivation, the bearing of the model on recent discussions of the so-called 'information paradox', and the implications of the model for the nature of space.

This article emerges from the broader intentions of a research-intervention project carried out in partnership with the municipal public network of Niterói at the same time that the city tries to respond to BNCC legal demands. From rounds of conversations with teachers in an extension course in order to contribute to the construction of the city's curriculum framework, we seek to configure a theoretical reflection on curriculum policy, modes of existence and diffraction. Situated as heirs of the tradition that criticized the distinction between implementation and formulation, we have developed the argument that instead of a curriculum going through a network, a network invariably goes through the curriculum. That is, a continuous topological dynamic comes alive, involving spatiotemporal variation. Anchored in feminist and queer studies of science and technology and by intersections of Gilles Deleuze's philosophy, we point out how a constitutive differentiation of politics exhibits a diffraction of time and space and, at the same step, constitutes ontological entanglements in which modes of existence render possible, involving subjectivity and otherness. We therefore defend the urgency of problematizing the teleology of educational discourse, which, by planning space and quantifying time, converts this inalienable diffraction of politics into a purge of difference. Far from redemption, it is about reactivating the vital importance of curriculum policy as an active participant in the becoming of the world without which there will be no possible democracy., Este artigo emerge das intenções mais gerais de um projeto de pesquisa-intervenção realizado em parceria com a rede pública municipal de Niterói no mesmo momento em que o município experimenta responder as demandas legais da BNCC. A partir de rodas de conversas com professores de um curso de extensão com a finalidade de contribuir com a construção do referencial curricular da cidade, buscamos configurar uma reflexão teórica sobre política de currículo, modos de existência e difração. Situados como herdeiros da tradição que criticou a distinção entre implementação e formulação, desenvolvemos o argumento de que, ao invés de um currículo passar por uma rede, uma rede invariavelmente passa pelo currículo. Isto é, uma dinâmica topológica contínua ganha vida, envolvendo a variação espaço-temporal. Ancorados em estudos feministas e queers da ciência e da tecnologia e por intersecções da filosofia de Gilles Deleuze, indicamos que um diferimento constitutivo da política exibe uma difração do tempo e do espaço e, no mesmo passo, constitui emaranhados ontológicos nos quais modos de existência tornam-se possíveis, envolvendo subjetividade e alteridade. Defendemos, portanto, a urgência de estranhar a teleologia do discurso educacional que, ao planificar o espaço e quantificar o tempo, converte essa inalienável difração da política em expurgo da diferença. Longe da redenção, trata-se de reativar a importância vital da política curricular como participante ativa do devir do mundo sem o qual não haverá democracia possível., El artículo emerge de las intenciones más generales de un proyecto de intervención-investigación en asociación con la red pública municipal de Niterói al mismo tiempo que la ciudad responde a las demandas legales de la BNCC. Desde rondas de conversaciones con los maestros de un curso de extensión con la finalidad de hacer contribuciones a la construcción del marco curricular de la municipalidad, intentamos dibujar una reflexión teórica sobre la política curricular, los modos de existencia y la difracción. Ubicados como herederos de la tradición que criticaba la diferencia entre implementación y formulación, desarrollamos el argumento de que, en lugar de un currículo pasar por una red, una red pasa invariablemente por el currículo. Es decir, una dinámica topológica continua gana vida, implicando la variación espacio-temporal. Haciendo uso de estudios feministas y queers, de la ciencia y la tecnología y de intersecciones de la filosofía de Gilles Deleuze, señalamos que un aplazamiento constitutivo de la política exhibe una difracción de tiempo y espacio y, al mismo paso, constituye enredos ontológicos tornando modos de existencia posibles, involucrando, por supuesto, subjetivad y alteridad. Defendemos, así, la urgencia de cuestionar la teleología del discurso educativo que, al planificar el espacio y cuantificar el tiempo, convierte esta difracción inalienable de la política en exclusión de la diferencia. Lejos de la redención, tratamos de reactivar la importancia vital de la política curricular como participante activo en el futuro del mundo sin el cual no habrá democracia posible.

Over a century since its inception, general relativity continues to lie at the heart of some of the most researched topics in theoretical physics. It seems likely that the coveted solutions to problems like quantum gravity are to be found in an extension of general relativity, one which may only be visible in an alternate formulation of the theory. In this thesis we consider the possibility of casting general relativity in the form of an initial value problem where spacetime is seen as the evolution of space. This evolution is shown to be constrained and of Hamiltonian type. Not all spacetimes are physically acceptable. To be compatible with particle physics, one would like spacetime to accommodate fermions. Here we can take comfort in Geroch’s theorem, which implies that any spacetime that admits a Hamiltonian formulation automatically supports the existence of fermions. We review the elements that go into the proof of this theorem., Allmän relativitetsteori har i över hundra år legat i teoretiska fysikens framkant. Det är möjligt att lösningarna på öppna problem som kvantiseringen av gravitation går att finna i en utvidgning av allmän relativitetsteori – och kanske uppenbarar sig denna utvidgning bara ur en alternativ formulering av teorin. I den här uppsatsen formuleras allmän relativitetsteori och dess Einsteinekvationer som ett begynnelsevärdesproblem, genom vilket rumtiden kan betraktas som rummets historia. Vi visar att rummets rörelseekvationer är Hamiltons ekvationer med tvångsvillkor. Enligt partikelfysiken bör fermioner kunna finnas till i rumtiden. Härom kan vi åberopa Gerochs sats, enligt vilken rumtider som har en Hamiltonsk formulering också medger fermioner. Vi redogör för huvuddragen i beviset av Gerochs sats.

8.962 is MIT's graduate course in general relativity, which covers the basic principles of Einstein's general theory of relativity, differential geometry, experimental tests of general relativity, black holes, and cosmology.

In light of recent developments in nearly AdS(2) holography, we revisit the semi-classical version of two-dimensional dilaton gravity proposed by Callan, Giddings, Harvey, and Strominger (CGHS) [1] in the early 90's. In distinction to the classical model, the quantum-corrected CGHS model has an AdS(2) vacuum with a constant dilaton. By turning on a non-normalizable mode of the Liouville field, i.e. the conformal mode of the 2d gravity, the explicit breaking of the scale invariance renders the AdS(2) vacuum nearly AdS(2). As a consequence, there emerges an effective one-dimensional Schwarzian-type theory of pseudo Nambu-Goldstone mode-the boundary graviton-on the boundary of the nearly AdS(2) space. We go beyond the linear order perturbation in non-normalizable fluctuations of the Liouville field and work up to the second order. As a main result of our analysis, we clarify the role of the boundary graviton in the holographic framework and show the Virasoro/Schwarzian correspondence, namely that the 2d bulk Virasoro constraints are equivalent to the graviton equation of motion of the 1d boundary theory, at least, on the SL(2, R) invariant vacuum.

U savremenoj fizici, sa pojavom teorije relativiteta i kvantne mehanike, kao i u novijim teorijama kvantne gravitacije, pojavljuju se najrazličitije strukture prostor-vremena, što čini objašnjenje pojma prostor-vremena pravim izazovom. Jedno novije predloženo rešenje jeste funkcionalističko, sa geslom "prostor-vreme jeste ono što prostor-vreme radi". Ideja je da su fizičko polje ili neki objekat prostorno-vremenski zahvaljujući tome što igraju određenu ulogu u teoriji. Različiti istraživački programi koji se bave kvantnom gravitacijom rađaju nove dileme vezane za ove pojmove - pojavljuje se mogućnost da se prostor i vreme uopšte ne jave kao deo fundamentalne ontologije teorije. Funkcionalizam može da odgovori na ove izazove. Ovo objašnjenje prostor-vremena takođe može da baci novo svetlo na stare filozofske rasprave, poput one između supstantivista i relacionista ili realista i anti-realista., In contemporary physics, from General relativity and Quantum mechanics to new research programs of Quantum gravity, we can find a vast variety of spacetime structures, which makes the interpretation of this concept a real challenge. Recently, a group of authors advanced a new interpretation of spacetime called 'spacetime functionalism', with the idea that spacetime should be defined via its functional role in the physical theory, in other words, "spacetime is what spacetime does". A material field or an object are spatiotemporal if they play a defined role in a physical theory. The approach is meant to be widely applicable, from classical mechanics to possible new theories of Quantum gravity, where spacetime might not appear at the fundamental theory level. Functionalism can be well combined with the emergent spacetime. It should also shed a new light on traditional philosophical debates between substantivists and relationists and between realists and anti-realists.

We live today the centenary of Eddington contribution to verify that gravity acts on light trajectories. This change of paradigm is reflected in the circle of ideas that evolves in the "science of vision" that underlies the history of painting., Hace ahora cien años que Eddington constató que la gravedad, tal como predecía Einstein, afecta a las trayectorias luminosas. Este cambio de paradigma científico se refleja en la historia de la "ciencia de la visión" que acompaña en gran medida al desarrollo de la pintura.

Social time is an objective virtual reality; it unites the biological, psychological and social life of humans. It is also a mode of existence of culture and of organizing social interactions and vital activity. Spatial communities evolving over a long time on certain territories have stable economic, social, political and spiritual ties, relations and synergies localized in time. The interdisciplinary concept of time which is not well studied does not permit an assessment of importance of this social resource for the development of communities. The present paper is an attempt to develop a research discourse on the impact of temporal parameters on spatial communities in provincial regions. The social time of a spatial community has two measurement vectors: chronological and temporal. The chronological vector permits a study of spatial communities (like urban and country dwellers) according to certain metrics like duration, length of existence and of functioning, rate of social processes, the sequence of development stages, the biography of a spatial community. Timing, the sense of time, temporal values, emotional experience and filling the time with events – these and other characteristics build temporal ties and relations within a spatial community. Changing the attitude to time as a resource of spatial communities that can be capitalized and converted is of practical importance for effective governance. Satisfaction with the place they exist in, enhancing the quality of life, developing spatial and temporal advantages of a region, activity of regional and municipal authorities, improving their reputation, and building trust are conditions for and important social resources in overcoming social inequality which shows, among others, spatial characteristics as well. All these factors are necessary to bring new life to the regions., Социальное время является объективной виртуальной реальностью, соединяющей биологическую, психологическую и социальную жизнь человека, формой существования человеческой культуры и организации социальных взаимодействий и жизнедеятельности. Территориальные общности, формирующиеся длительное время на определенной территории, имеют устойчивые экономические, социальные, политические, духовные связи, отношения и взаимодействия, локализованные во времени. Мало разработанный, междисциплинарный концепт времени на сегодняшний день не позволяет оценить значимость данного социального ресурса для развития территорий. В статье предпринята попытка сформировать исследовательский дискурс влияния темпоральных характеристик на территориальные общности провинциальных регионов. Социальное время территориальной общности имеет два вектора измерения – хронологический и темпоральный. Хронологический вектор позволяет рассмотреть территориальные общности (например, жителей городов и сельских поселений) согласно метрическим показателям: продолжительность, длительность существования и функционирования, скорость социальных процессов, последовательность этапов развития, «биографию» территориальной общности. Темпоритмы, «чувство времени», темпоральные ценности, эмоциональное переживание и наполнение времени событиями, – эти и другие характеристики образуют темпоральные связи и отношения территориальных общностей. Изменение отношения к времени как ресурсу территориальных общностей, способному капитализироваться, конвертироваться, имеет практическое значение для эффективного управления территориями. Удовлетворенность территориальных общностей местом своего проживания и взаимодействия в настоящем и будущем, повышение качества жизни, развитие пространственных и временных преимуществ региона, деятельность региональной и муниципальной власти, улучшение ее репутации, формирование доверия, – являются условиями и важными социальными ресурсами преодоления социального неравенства, имеющего, в том числе, и те

In this paper, some conceptual issues are addressed in order to make sense of what string theory is supposed to tell us about spacetime. The dualities in string theory are used as a starting point for our argumentation. We explore the consequences of a standard view towards these dualities, namely that the dual descriptions represent the same physical situation. Given this view, one has to understand string theory in a manner such that what counts as physical spacetime is based only on the shared physical content—or common core—of the dual descriptions. In general such a spatiotemporal picture does not have to agree with, or be similar to, any of the ones suggested by naïve readings of the dual descriptions. However, in certain regimes or limits, one or the other of the initial dual descriptions may give a good effective description of physical spacetime.

This article is a logical analysis of historical records and reaches conclusions that are original. Prior to 1905 it was generally believed that the universe had always existed. The exact age of Earth was not known. The luminiferous æther theory explained how light was able to propagate through empty space. In 1930 Alfred Korzybski published his book “Science and Sanity”. In it he originated his aphorism —The Map is not the Territory. Reality consists of physical reality — the territory— and observed reality — the map. The Rossi-Hall experiment demonstrated that time dilation occurs physically and cannot be observed directly. The universe came into existence when the big bang occurred. When photons came into being, time came into being. All mechanisms for measuring time experience time dilation. The big bang caused major changes to science’s understanding of the nature of the universe. The speed of a photon through space equals a Planck length divided by a Planck time. We don’t really measure time, what we measure is the effect that time has on the instruments used to measure time. Everything; in Relative Time is based on observers. If you remove all references to observers from either Special Relativity or Spacetime there is almost nothing left. When the concepts of relative time were originated, no thought was given to the possibility that time might consist of both observed time and physical time. Photons — and the resulting time — came into existence with the big bang The movement of photons thru spacetime constitutes absolute time Without events, nothing happens. Every event has a frame of reference. ‘Now’ can occur in physical time and in observed time. A physical event always results in a physical ‘now’. Every event must have a frame of reference. Objects that move through space experience time dilation but they do not observe it. The observation of each observer is unique for that observer and need not be the same as either the actual event itself or the obs

In this report, we will give the first constraints on in-matter nonmetricity. We will show how the effective-field-theory (EFT) toolbox developed for the study of Lorentz violation (LV) can be employed for investigations of the "effective LV" background caused by nonmetricity, a geometric object extending the notion of a Riemannian manifold. The idea is to probe for the effects of spacetime nonmetricity sourced by liquid 4He with polarized slow neutrons. We present the first constraints on isotropic and parity-odd nonmetricity components. Further constraints on anisotropic nonmetricity components within this EFT framework may be feasible with proper experimental techniques in the near future. © Published under licence by IOP Publishing Ltd.

The concept of spacetime has long been used in physics to refer to models that integrate 3D space and time as a single 4D continuum. We argue in this paper that it is also advantageous to use this concept in a practical geographic context by realizing a true 4D model, where time is modeled and implemented as a dimension in the same manner as the three spatial dimensions. Within this paper we focus on 4D vector objects, which can be implemented using dimension-independent data structures such as generalized maps. A 4D vector model allows us to create and manipulate models with actual 4D objects and the topological relationships connecting them, all of which have a geometric interpretation and can be constructed, modified, and queried. In this paper we discuss where such a 4D model fits with respect to other spatiotemporal modeling approaches, and we show concretely how higher-dimensional modeling can be used to represent such 4D objects and topological relationships. In addition, we explain how the 4D objects in such a system can be created and manipulated using a small set of implementable operations, which use simple 3D space and 1D time inputs for intuitiveness and which modify the underlying 4D model indirectly., Urban Data Science

Microstates of multiple collinear black holes embedded in a non-collinear two-center Taub-NUT spacetime are sought in 4 dimensions. A set of coupled partial differential equations are obtained and solved for almost-BPS states, where some supersymmetry is preserved in the context of N = 2 supergravity in 4 dimensions. The regularity of solutions is carefully considered, and we ensure that no CTC (closed time-like curves) are present. The larger framework is that of 11-dimensional N = 2 supergravity, and the current theory is obtained by compactifying it down to 4 dimensions. This work is a generalization (to three non-collinear centers) of a previous paper by Bena et al.

Einsteins theory of General relativity is a popular theory, but unfortunately it cannot account for all the observable gravity in the universe. This paper presents a new force predicted through the McMahon field theory (2010) [1], which is refered to in McMahon field theory (2010) [1] as Mahona (pronounced Maa-naa), which appears to be gravitational. In this paper, I draw upon the McMahon field theory (2010) [1], and use it to explain why mass appears gravitational, as well as the source of the excess gravity that General relativity cannot account for. I will do this in simplistic terms for the benefit of the reader. Thus with the understanding presented here, any vechicle utilising this new force called Mahona shall have gravitational capability.

Tato práce se věnuje problematice železničních nádraží jako kulturním fenoménům a jejich zobrazení v česky psaných prózách do počátku dvacátého století do počátku století jedenadvacátého. Práce zároveň akcentuje zobrazení vlakových stanic i v dalších uměleckých druzích. Těžiště práce je intepretaci uměleckých děl, v nichž zaujímá nádražní časoprostor stěžejní roli., This thesis focuses on issue of railway stations as cultural phenomena a their portrayal in Czech prose since the beginning of 20th century until the beginning of 21st century. Thesis also accentuates portrayal of railway stations in other artistic forms. A core of this thesis lies in interpretation of works of art, in which railway setting plays the key role., Fakulta filozofická

The principle postulate of general relativity appears to be that curved space or curved spacetime is gravitational, in that mass curves the spacetime around it, and that this curved spacetime acts on mass in a manner we call gravity. Here, I use the theory of special relativity to show that curved spacetime can be non-gravitational, by showing that curve-linear space or curved spacetime can be observed without exerting a gravitational force on mass to induce motion- as well as showing gravity can be observed without spacetime curvature. This is done using the principles of special relativity in accordance with Einstein to satisfy the reader, using a gravitational equivalence model. Curved spacetime may appear to affect the apparent relative position and dimensions of a mass, as well as the relative time experienced by a mass, but it does not exert gravitational force (gravity) on mass. Thus, this paper explains why there appears to be more gravity in the universe than mass to account for it, because gravity is not the resultant of the curvature of spacetime on mass, thus the dark matter and dark energy we are looking for to explain this excess gravity doesn't exist.

In this thesis, we explore the subject of complex spacetimes, in which the mathematical theory of complex manifolds gets modified for application to General Relativity. We will also explore the mysterious Newman-Janis trick, which is an elementary and quite short method to obtain the Kerr black hole from the Schwarzschild black hole through the use of complex variables. This exposition will cover variations of the Newman-Janis trick, partial explanations, as well as original contributions.

This dissertation explores in particular a few ways in which similarity bears on general relativity, our best physical theory of space and time. The first way concerns the role of the concept of “physicality” in theorizing and using spacetime models, which manifests in at least two different ways. One is whether particular models are (or have properties that are) “physically unreasonable“—they are deemed to be pathological or otherwise artifactual, and so must excluded from the theory. Another is whether particular properties of those models are “physically significant”—warranted to be inferred about the properties of a physical system they represent. This distinction, which I draw in more detail in chapter 2, separates these two senses of physicality, the former modal-metaphysical and the latter inferential-epistemic. It is this latter that more intimately involves the notion of similarity, particular notions of which can be encoded through the use of topology. I argue then that there is no canonical topology on the models of general relativity. Rather, the choice of topology must be nontrivially dependent on the context of investigation.In chapter 3, I bring attention to another way in which similarity, as encoded in topology, can be put to substantive use, namely in better understanding the nature of the reductive relationship between general relativity and its predecessor, the Newtonian theory of space, time, and gravitation. In particular, I show how this relationship can be made both perfectly general—applying to any situation the theories describe—and explanatory of the Newtonian theory's success.Finally, in chapter 4, I explicate what I think are the deeper structural issues with certain examples due to Robert Geroch that are intended to show a certain topology commonly used in the physics literature in fact has several counterintuitive features. I show that there is in fact no topology that meets a strong version of Geroch's demands, but if those demands ar

Gravity is the curvature of spacetime, the structural property of static gravitational field, a geometric field, in curved coordinates, according the functions guv, that express geometric relations. Course, general relativity is a relational theory, however, gravity, a thinking category, has symetric physical effects with matter. Throught of relativist aether was attempted transform spacetime in a substantia without succes, the consequence was return to problematic geometric field. The philosophy of the science intervenes, and according the substantialist theory spacetime is a inmaterial, geometric substantia. Then, the metaphysics arrives to a full solution in the super-substantivalist theory, that affirms: matter arises from geometric spacetime. Thus, it explains consistently the symetric physical effects between spacetime and matter. Surely, this solution is a medieval speculation. Our goal is driver the debate on gravity, to the arena of the quantum physics, but without the ballast of the general relativity.&nbsp

The universe has two main dimensions spatial dimension (consists of three dimensions directional X, Y, Z) and the other dimension is the temporal dimension. Time and space are linked strongly inseparable so we will consider the time and place one  Is the dimension of spacetime (as proved Einstein in his theory of relativity). Spacetime dimension includes the temporal dimension and spatial dimension (the three dimensions of space). Spacetime dimension two (real spacetime Vision spacetime). Spacetime has two cases:  1- Navigate spacetime 2- The change in spacetime. spacetime is Personally like a fingerprint and it always variable ( everyone has Personally spacetime and there are not find two of spacetime are the same.

This thesis contributes with a countryside perspective to queer research by highlighting the countryside as a context where queer lives are lived. In the thesis I problematize the city/countryside divide with a view of the concept of queer as dependent on space and time. The empirical materials are generated through a workshop on queerness, gathering people living within a countryside context; the materials consist of a discussion and written responses to questions on queerness and the city/countryside binary. Theoretically and methodologically, the thesis is inspired by the notion of agential realism (Barad 2007) and situated knowledge, (Haraway 1988); the use of creative writing, inspired by Richardson (1994 and 2000), has also been central to the development of the thesis. The analysis is carried out within themes focusing on conditions for queerness within city/countryside experienced by people situated in the countryside. The analysis shows how space, time, contexts and intersections are entangled and queering the city/countryside divide.

A recently developed technique known as analogue transformation acoustics has allowed the extension of the transformational paradigm to general spacetime transformations under which the acoustic equations are not form invariant. In this paper, we review the fundamentals of analogue transformation acoustics and show how this technique can be applied to build a device that increases the density of events within a given spacetime region by simultaneously compressing space and time.

Theoretical and methodological framework Sociocultural and postcolonial perspectives on culture, language and identity allow us to empirically investigate how students in cyber communities negotiate and co-construct SpaceTime as a single dimension during the institutionally framed agenda of an online language course focused in this study. Here ‘correct’ languaging or language-use is both a means and a goal in itself. Students gather from all over the world to access the virtual classroom in order to participate and learn the target language. In the online space of the virtual classroom, there is no common locality beyond the pieces of local spaces that individuals can enter. This entering shapes the encounters inside the shared space of the virtual classroom. Such disrupted space is what frames (in terms of constraints and affordances) participation and learning in cyber communities. We argue that in order to understand and empirically study such encounters (or sites of engagement) it is fruitful to use the epistemological lenses of TimeSpace as well as the postcolonial concepts of Third Space and Hybridity. This, we argue, allows us an analytical shift in focus, from what happens inside a space or a community, to what occurs at the boundaries, in-between (virtual) spaces. This is done through a multi-scale analysis of mundane interaction at the micro and meso scales. An augmented conversation analysis (CA) of the interaction at the micro scale allows us to attend to the transmodal and translingual nature of the online encounters. The analysis at the meso scale permits a mapping of the interpenetration of students’ geopolitical spaces in the online site to understand the ways in which students’ (im)mobilities are afforded and constrained by/in cyber educational spaces. Research questions Our interests here relate to accounting for how students make sense of the transnational, -lingual, -modal nature of the virtual classroom of which they are members. Going beyon, Projektets hemsida www.oru.se/ccd/cincle, CINLE

As Galileo peered through a lens to see the twinkle of the Jovian moons, and Antonie Van Leeuwenhoek did the same to study the tremulous basis of all life, so the fabric of threads we weave across time and space – the vast net of relations that bind and separate us – is visible only through a lens. Footprints in the snow and the weathered stone steps of buildings hint at the shape of these threads, but the coming of spring and the hardness of stone limit our observations. The Global Positioning System (GPS) now provides us a lens to see the path that individuals, families, and communities take in space-time -- their worldlines. When millions of GPS signatures are collected from hundreds of individuals, heritable patterns emerge that embody particular individual’s ideas and practices, as well as those of the society and the environment in which they operate. Besides providing a tool to test assumptions about how space is used, I argue in this thesis that by allowing us to glimpse a terra incognita, mapping worldlines also provides a unique perspective on our spatial relationship to one another.

This thesis proposes and develops much of the groundwork for a model of emergent physics, posited to describe the initial condition and early evolution of a universe. Two different considerations motivate the model. First, the spacetime manifold underlying general relativity and quantum theory is a complex object with much structure, but its origin is unexplained by the standard picture. Second, it is argued, the usual assumption of the preexistence of this manifold leads to possibly intractable theoretical (not observational) difficulties with the usual cosmological inflation idea. Consistent with both considerations, the assumption of a manifold that precedes a big bang cosmology is dropped; instead, a spacetime manifold with metric, Lorentz symmetry, and manifestation of standard quantum fields propagating on the spacetime all emerge in the model from a simpler, statistically scale invariant underlying structure, driven by an inflation-like process. The basic structural components of the model are a stochastic (not quantum or classical) scalar field on a general metric space, plus a collection of quantum fields that supply the matter content once spacetime begins to emerge. Importantly, standard quantum fields cannot be defined on the pre-emergent space; this is addressed by assuming quantum theory exists a priori, and then postulating that quantum fields can begin to manifest once an approximate spacetime has emerged. Atypical fluctuations in the scalar field transiently break the statistical scale invariance in a localized region of the general metric space; a very small subset have field configurations of approximate spacetimes which can potentially evolve into an initial condition for a universe. Spacetime structure and geometry then arise from the dependence of propagation speeds and spatial/temporal distances on variations in the scalar field; these variations are seeded by the matter (quantum) fields. The thesis develops the mathematics of the basic compon

The gravitational redshift forms the central part of the majority of the classical tests for the general theory of relativity. It could be successfully checked even in laboratory experiments on the earths surface. The standard derivation of this effect is based on the distortion of the local structure of spacetime induced by large masses. The resulting gravitational time dilation near these masses gives rise to a frequency change of any periodic process, including electromagnetic oscillations as the wave propagates across the gravitational field. This phenomenon can be tackled with classical electrodynamics assuming a curved spacetime background and Maxwells equations in a generally covariant form. In this paper, we show that in a classical field theoretical context the gravitational redshift can be interpreted as the propagation of electromagnetic waves in a medium with corresponding conductivity ¿ = g/(¿ 0c 3), where g is the gravitational acceleration and ¿ 0 is the vacuum magnetic permeability. Moreover, the energy density of the wave remains proportional to its frequency in agreement with Plancks postulate. © 2012 IOP Publishing Ltd.

We present an audio-visual Virtual Reality display system for simulated sound fields. In addition to the room acoustic simulation by means of phonon tracing and finite element method this system includes the stereoscopic visualization of simulation results using a 3D back projection system as well as auralization by use of a professional sound equipment. For auralization purposes we develop a sound field synthesis approach for accurate control of the loudspeaker system.

This paper provides a survey of approaches for special relativistic visualization. Visualization techniques are classified into three categories: Minkowski spacetime diagrams, depictions of spatial slices at a constant time, and virtual camera methods that simulate image generation in a relativistic scenario. The paper covers the historical outline from early hand-drawn visualizations to state-of-the-art computer-based visualization methods. This paper also provides a concise presentation of the mathematics of special relativity, making use of the geometric nature of spacetime and relating it to geometric concepts such vectors and linear transformations.

The relation between uniformly accelerated reference frames in flat spacetime and the uniform gravitational field is examined in a relativistic context. It is shown that contrary to previous statements, equivalence does not break down in this context. No restrictions to Newtonian approximations or small enclosures are necessary.