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It has been shown that the theory of relativity can be applied physically to the functioning brain, so that the brain connectome should be considered as a four-dimensional spacetime entity curved by brain activity, just as gravity curves the four-dimensional spacetime of the physical world. Following the most recent developments in modern theoretical physics (black hole entropy, holographic principle, AdS/CFT duality), we conjecture that consciousness can naturally emerge from this four-dimensional brain connectome when a fifth dimension is considered, in the same way that gravity emerges from a 'flat' four-dimensional quantum world, without gravitation, present at the boundaries of a five-dimensional spacetime. This vision makes it possible to envisage quantitative signatures of consciousness based on the entropy of the connectome and the curvature of spacetime estimated from data obtained by fMRI in the resting state (nodal activity and functional connectivity) and constrained by the anatomical connectivity derived from diffusion tensor imaging. [ABSTRACT FROM AUTHOR]

We review some semantical aspects of probability bounds from Boole's "conditions on possible experience" violated by quantum mechanics. We also speculate about emerging space-time categories as an epiphenomenon of quantization and the resulting breakdown of relativity theory by non-unitary and non-linear processes. [ABSTRACT FROM AUTHOR]

We explore the tripartite entropic uncertainty and genuine tripartite quantumness of Dirac fields in the background of the Garfinkle–Horowitz–Strominger (GHS) dilation space-time. It is interesting to note that Hawking radiation leads to the decay of quantum nonlocality in the physically accessible region while preserving its total coherence. More importantly, it demonstrates an intrinsic trade-off relationship between the coherences of physically accessible and inaccessible regions. Moreover, we examine the effect of Hawking radiation on entropy-based measured uncertainty and find that stronger Hawking radiation causes the uncertainty in physically accessible regions to increase while decreasing the uncertainty in physically inaccessible regions. Therefore, our investigations may be beneficial to a better understanding of the system's quantumness in a curved space-time. Combining relativity theory with quantum information science offers new avenues for comprehending the information paradoxes involving black holes. [ABSTRACT FROM AUTHOR]

This article introduces a new field theory formulation. The new field theory formulation recognizes vector continuity as a general principle and begins with a field that satisfies vector continuity equations. Next, independent of the new formulation, this article introduces a new space-time adjustment. Then, we solve the one-body gravitational problem by applying the space-time adjustment to the new field theory formulation. With the space-time adjustment, the new formulation predicts precisely the same precession of Mercury and the same bending of light as general relativity. The reader will find the validating calculations to be simple. The equations of motion that govern the orbital equations are in terms of Cartesian coordinates and time. An undergraduate college student, with direction, can perform the validations. [ABSTRACT FROM AUTHOR]

I present an argument against a relational theory of spacetime that regards spacetime as a 'structural quality of the field'. The argument takes the form of a trilemma. To make the argument, I focus on relativistic worlds in which there exist just two fields, an electromagnetic field and a gravitational field. Then there are three options: either spacetime is a structural quality of each field separately, both fields together, or one field but not the other. I argue that the first option founders on a problem of geometric coordination and that the second and third options collapse into substantivalism. In particular, on the third option it becomes clear that the relationalist's path to Leibniz equivalence is no simpler or more straightforward than the substantivalist's. 1 Introduction 2 Background 2.1 Relational theories of spacetime 2.2 Brief remarks on general relativity 3 First Horn: Geometric Coordination 4 Second Horn: Problems of Coincidence 5 Third Horn: General Relativity and Gauge 5.1 Preventing collapse 5.2 The revised shift argument 6 Conclusion [ABSTRACT FROM AUTHOR]

Abstract In 2018, the Congress of the Philippines is expected to pass the Philippine Space Development Act , leading to the adoption of the first national space policy in the country and the establishment of the Philippine Space Agency (or PhilSA). This historic event is the final outcome of a long process involving various stakeholders in the Philippines from government, academia and industry. This article provides the first comprehensive history of this process from its inception in the late 20th century until now, with a specific focus on its acceleration since 2013. It also investigates the future expectations of the national space development program, in particular regarding the development of a local space industry. Apart from solely describing the history of the Philippines, this paper presents more generally the case of a developing country willing to gain a foothold in space. In comparison with existing literature on space development programs focusing exclusively on rich western countries or powerful emerging nations, this paper provides other developing countries with highly valuable information by describing such a transparent, balanced and promising initiative as the Philippine space development program. Highlights • The Philippine Space Policy is balanced and perfectly fits the needs of the country. • The process of developing the Philippine space policy can inspire other countries. • Private sector's involvement is crucial for the success of the future space program. • The Filipino space policy's parliamentary approval is expected for late 2018. • Initiating a space program is feasible and recommended for developing countries. [ABSTRACT FROM AUTHOR]

In the R-Minkowski space-time, which we recently defined from an appropriate deformed Poisson brackets that reproduce the Fock coordinate transformation, we derive an extended form for Maxwell's equations by using a generalized version of Feynman's approach. Also, we establish in this context the Lorentz force. As in deformed special relativity, modifying the angular momentum in such a way as to restore the R-Lorentz algebra generates the magnetic Dirac monopole. [ABSTRACT FROM AUTHOR]

Einstein acknowledged that his reading of Hume influenced the development of his special theory of relativity. In this article, I juxtapose Hume's philosophy with Einstein's philosophical analysis related to his special relativity. I argue that there are two common points to be found in their writings, namely an empiricist theory of ideas and concepts, and a relationist ontology regarding space and time. The main thesis of this article is that these two points are intertwined in Hume and Einstein. [ABSTRACT FROM AUTHOR]

Fanny-Leicht Gymnasium Stuttgart, Fanny-Leicht Str. 13, 70563 Stuttgart-Vaihingen, Germany In an advanced course on general relativity, some exotic spacetimes like wormholes with a more complex topology than the standard Schwarzschild spacetime can be studied in detail. In this regard, it has been pointed out by Morris and Thorne that wormholes could be a valuable tool for teaching general relativity. In this paper, we claim rotating wormholes might also have a pedagogical role in general relativity, and present an empirical approach to explore periodic orbits of such, that could be applied also to other spacetimes. [ABSTRACT FROM AUTHOR]

By transforming a compressible fluid into an incompressible fluid, one can derive the Lorentz transformation from the Galilean transformation. This proves that there is a special superfluid linked to relativity, compressible in absolute space-time theory and incompressible in relativistic space-time theory. This special universal superfluid is just the macroscopic physical vacuum, and light is a second sound disturbance in it. The absolute and relativistic space-time theories are two different space-time theories in nature. A change of vacuum density in absolute space-time theory causes a change in the actual space-time standard, and, thus, relativistic effects occur. There are certain discrepancies and corresponding relations between these two space-time theories. [ABSTRACT FROM AUTHOR]

In general relativity, gravitational collapse of matter fields ends with the formation of a spacetime singularity, where the matter density becomes infinite and standard physics breaks down. According to the weak cosmic censorship conjecture, singularities produced in the gravitational collapse cannot be seen by distant observers and must be hidden within black holes. The validity of this conjecture is still controversial and at present we cannot exclude that naked singularities can be created in our Universe from regular initial data. In this paper, we study the radiation emitted by a collapsing cloud of dust and check whether it is possible to distinguish the birth of a black hole from the one of a naked singularity. In our simple dust model, we find that the properties of the radiation emitted in the two scenarios is qualitatively similar. That suggests that observational tests of the cosmic censorship conjecture may be very difficult, even in principle. [ABSTRACT FROM AUTHOR]

We consider a free particle in a de Sitter spacetime. We use a picture in which the analogs of the Schrödinger operators of the particle are independent of both the time and the space coordinates. These operators induce operators which are related to Killing vectors of the de Sitter spacetime. [ABSTRACT FROM AUTHOR]

This is an extended version of my lecture at the LIII Cracow School of Theoretical Physics in Zakopane in which I presented the results of joint work with P. Bizoń (Phys. Rev. Lett. 111, 041102 (2013)) concerning (in)stability of the three-dimensional anti-de Sitter spacetime. [ABSTRACT FROM AUTHOR]

Lorentz pointed out in 1899 that a relativistic space-time transformation which leaves Maxwell's equations invariant could only be defined to within a common factor on the basis of then-existing experimental data. The present work calls attention to the fact that Einstein's subsequent derivation of the Lorentz transformation (LT) is based on an undeclared assumption regarding the functional dependence of this factor. Consequently, many of the unconfirmed predictions of Einstein's special theory of relativity (STR), such as the remote nonsimultaneity of events and the symmetric relationship of measurements made by observers in different inertial systems, would lose their validity if the above assumption is shown to be incorrect. At the same time, any other choice for Lorentz's common factor is seen to be consistent with the relativistic velocity transformation (VT). Accordingly, predictions of STR that are derived exclusively from the VT would not be affected by such a change in relativity theory. On this basis, an alternative Lorentz transformation is defined that also satisfies Einstein's two postulates of relativity, but incorporates the strict proportionality of the rates of moving clocks assumed in the operation of the Global Positioning System (GPS) rather than invoking the inextricable mixing of space and time coordinates predicted by the LT. [ABSTRACT FROM AUTHOR]

Any spacetime containing a degenerate Killing horizon, such as an extremal black hole, possesses a well-defined notion of a near-horizon geometry. We review such near-horizon geometry solutions in a variety of dimensions and theories in a unified manner. We discuss various general results including horizon topology and near-horizon symmetry enhancement. We also discuss the status of the classification of near-horizon geometries in theories ranging from vacuum gravity to Einstein--Maxwell theory and supergravity theories. Finally, we discuss applications to the classification of extremal black holes and various related topics. Several new results are presented and open problems are highlighted throughout. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the role of wet dark fluid (WDF) in Kantowski-Sachs space-time in the general theory of relativity. In this theory, we solved the field equations for the case where ρWDF = -2pWDF . Various physical and geometrical properties of the model are also discussed. [ABSTRACT FROM AUTHOR]

Minkowski famously introduced the concept of a space-time continuum in 1908, merging the three dimensions of space with an imaginary time dimension ict, with the unit imaginary producing the correct spacetime distance x2-c2t2, and the results of Einstein's then recently developed theory of special relativity, thus providing an explanation for Einstein's theory in terms of the structure of space and time. As an alternative to a planar Minkowski space-time of two space dimensions and one time dimension, we replace the unit imaginary with the Clifford bivector i=e1e2 for the plane that also squares to minus one, but which can be included without the addition of an extra dimension, as it is an integral part of the real Cartesian plane with the orthonormal basis e1 and e2. We find that with this model of planar spacetime, using a twodimensional Clifford multivector, the spacetime metric and the Lorentz transformations follow immediately as properties of the algebra. This also leads to momentum and energy being represented as components of a multivector and we give a new efficient derivation of Compton's scattering formula, and a simple formulation of Dirac's and Maxwell's equations. Based on the mathematical structure of the multivector, we produce a semi-classical model of massive particles, which can then be viewed as the origin of the Minkowski spacetime structure and thus a deeper explanation for relativistic effects. We also find a new perspective on the nature of time, which is now given a precise mathematical definition as the bivector of the plane. [ABSTRACT FROM AUTHOR]

Fundamental physics began the twentieth century with the twin revolutions of relativity and quantum mechanics, and much of the second half of the century was devoted to the construction of a theoretical structure unifying these radical ideas. But this foundation has also led us to a number of paradoxes in our understanding of nature. Attempts to make sense of quantum mechanics and gravity at the smallest distance scales lead inexorably to the conclusion that spacetime is an approximate notion that must emerge from more primitive building blocks. Furthermore, violent short-distance quantum fluctuations in the vacuum seem to make the existence of a macroscopic world wildly implausible, and yet we live comfortably in a huge universe. What, if anything, tames these fluctuations? Why is there a macroscopic universe? These are two of the central theoretical challenges of fundamental physics in the twenty-first century. In this essay, I describe the circle of ideas surrounding these questions, as well as some of the theoretical and experimental fronts on which they are being attacked. [ABSTRACT FROM AUTHOR]

ABSTRACT Cosmological redshift z grows as the Universe expands and is conventionally viewed as a third form of redshift, beyond the more traditional Doppler and gravitational effects seen in other applications of general relativity. In this paper, we examine the origin of redshift in the Friedmann-Robertson-Walker (FRW) metrics with constant space-time curvature, and show that - at least for the static space-times - the interpretation of z as due to the 'stretching' of space is coordinate dependent. Namely, we prove that redshift may also be calculated solely from the effects of kinematics and gravitational acceleration. This suggests that its dependence on the expansion factor is simply a manifestation of the high degree of symmetry in FRW, and ought not be viewed as evidence in support of the idea that space itself is expanding. [ABSTRACT FROM AUTHOR]

We study static spherically symmetric spacetime to describe compact objects with anisotropic matter distribution. We express the system of Einstein field equations as a new system of differential equations using a coordinate transformation, and then write the system in another form with polytropic equation of state and obtain two classes of exact models. The models satisfy all major physical features expected in a realistic star. For polytropic index n = 2, we obtain expressions for mass and density which are comparable with the reported experimental observations. [ABSTRACT FROM AUTHOR]