In this work, the interior spacetime of stars is built in a Lorentz symmetry breaking model calle... more In this work, the interior spacetime of stars is built in a Lorentz symmetry breaking model called bumblebee gravity. Firstly, we calculated the modified Tolman-Oppenheimer-Volkoff equation in this context of modified gravity. Then we show that the bumblebee field, responsible for the symmetry breaking, increases the star mass-radius relation when it assumes its vacuum expectation value. When compared to the general relativity mass-radius relation, a Lorentz symmetry breaking context, like the bumblebee gravity, could provide more massive stars, surpassing the 2.5M⊙ limit as the interior of the star is described by quark matter with the MIT bag model.
Monthly Notices of the Royal Astronomical Society, 2023
The co-varying physical couplings (CPC) framework states that physical parameters like the speed ... more The co-varying physical couplings (CPC) framework states that physical parameters like the speed of light in vacuum c, the Newtonian constant G, and the cosmological constant Λ could indeed vary with the spacetime coordinates x µ. Here, we assume a temporal variation, that is, c(t), G(t) and Λ(t). We show that the McVittie spacetime, a black hole in an expanding universe, is a solution of the CPC framework providing naturally an important parameter of the model. Then, we calculate the shadow angular radius of this black hole at cosmological distances. A black hole shadow in the CPC context could be either larger or smaller than the same shadow in the standard cosmology. It depends on how the set {c, G, Λ} varies with time or with the cosmic expansion.
There have been three geometrizations in history. The first one is historically due to the Pythag... more There have been three geometrizations in history. The first one is historically due to the Pythagorean school and Plato, the second one comes from Galileo, Kepler, Descartes and Newton, and the third is Einstein's geometrization of nature. The term geometrization of nature means the conception according to which nature (with its different meanings) is massively described by using geometry. In this article, I focus on the third geometrization, in which the black hole shadow phenomenon provides an interesting statement about the level of geometrization achieved by the theory of general relativity. With the black hole shadow described by the Einsteinian theory, the geometrical interpretation of nature relates shape to dynamics or, more specifically, the shadow silhouette to the angular momentum, regardless the matter content inside the black hole. As a consequence, spacetime symmetry could play the role of the formal cause in black hole physics.
Following a recent approach in which the gravitational field equations in curved spacetimes were ... more Following a recent approach in which the gravitational field equations in curved spacetimes were presented in the Bopp–Podolsky electrodynamics, we obtained an approximate and spherically symmetric wormhole solution in this context. The calculations were carried out up to the linear approximation in both the spacetime geometry and the radial electric field. The solution presents a new parameter that comes from the Lagrangian of the model. Such a parameter was constrained by using the shadow radius of Sagittarius A*, recently revealed by the Event Horizon Telescope
Collaboration. Remarkably, the wormhole presented here is viable when its shadow is compared to the Sagittarius A* shadow.
Kasner cosmology is a vacuum and anisotropically expanding spacetime in the general relativity co... more Kasner cosmology is a vacuum and anisotropically expanding spacetime in the general relativity context. In this work, such a cosmological model is studied in another context, the bumblebee model, where the Lorentz symmetry is spontaneously broken. By using the bumblebee context it is possible to justify the anisotropic feature of the Kasner cosmology. Thus, the origin of the anisotropy in this cosmological model could be in the Lorentz symmetry breaking. Lastly, an application in the pre-inflationary cosmology is suggested.
The theory of regularity is a philosophical perspective in which laws of nature are just descript... more The theory of regularity is a philosophical perspective in which laws of nature are just descriptions, that is to say, laws of nature do not govern the world. Moreover, according to the theory of regularity, the number of laws of nature might be infinite, thus any attempt towards the theory of everything is doomed. Here I propose a special or restricted theory of regularity. The main difference as to the well-known version of that theory is both the range of validity and the scale of the laws of nature. Laws of nature ought to be considered just inside the observable universe and within certain energy and length scales. Even so I apply the theory of regularity to the multiverse scenario. As a consequence, the special theory of regularity supports only two types of multiverses by comparison with our world: those ones with a different sequence of unique events and different laws of nature and those ones with the same sequence of unique events and the same laws of nature instanced by the unique events. The latter case is some sort of eternal recurrence or a parallel eternal recurrence.
An effect of the Lorentz symmetry breaking is pointed out in the cosmological context. Using a Bi... more An effect of the Lorentz symmetry breaking is pointed out in the cosmological context. Using a Bianchi I geometry coupled to the Kalb-Ramond field, a consequence of the Lorentz symmetry violation is indicated by a different rate of expansion in a given spatial direction. This article focuses on the coupling constant ξ1, which generates, from the Kalb-Ramond field, all three coefficients that give rise to the Lorentz violation in the gravity sector of the minimal Standard Model Extension. The coupling constant ξ1 increases the rate of expansion of the universe in a given direction during a dark energy era. As a consequence, a range of validity of that coupling constant is also obtained.
Nietzsche colocou-se como um antípoda a Platão. Mas em questões cosmológicas, o eterno retorno ni... more Nietzsche colocou-se como um antípoda a Platão. Mas em questões cosmológicas, o eterno retorno nietzschiano tem também alguns pontos em comum à cosmologia platônica descrita no Timeu. A finitude espacial, a ciclicidade cósmica e a ética cosmológica dizem respeito às semelhanças, já a infinitude temporal, a teleologia e a necessidade afastam os filósofos. Então, neste trabalho, aponto proximidades e afastamentos entre os dois filósofos em questões cosmológicas, além de sugerir alguma atualidade de suas concepções em relação à nossa ciência. Como veremos, a relação entre ética e cosmologia ainda se mostra atual.
Following a recent approach, complete and analytic solutions (brane and bulk) of regular black ho... more Following a recent approach, complete and analytic solutions (brane and bulk) of regular black holes are shown in a brane context. The metrics are regular both on the four-dimensional brane and in the five-dimensional bulk. Like many brane world scenarios, the bulk spacetime is asymptotically anti-de Sitter. On the other hand, a de Sitter core on the brane avoids the singularity inside the event horizon, providing then well-known regular black holes on the brane. From the bulk perspective, the regular black holes are five-dimensional objects, with the event horizon extending to the extra dimension, but the de Sitter core is entirely on the four-dimensional brane.
Journal of Cosmology and Astroparticle Physics, 2021
In this work, a bumblebee field is adopted in order to generate cosmological anisotropies. For th... more In this work, a bumblebee field is adopted in order to generate cosmological anisotropies. For that purpose, we assume a Bianchi I cosmology, as the background geometry, and a bumblebee field coupled to it. Bumblebee models are examples of a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. When coupled to the Bianchi I geometry, which is not in agreement with a cosmological principle, the bumblebee field plays the role of a source of anisotropies and produces a preferred axis. Thus, a fraction of the cosmic anisotropies would come from the Lorentz symmetry violation. In the last part of the article, we try to assume an upper bound on the bumblebee field using the quadrupole and octopole moments of the cosmic microwave background radiation.
A mais comentada imagem científica em 2019 foi a imagem de M87*, buraco negro supermassivo centra... more A mais comentada imagem científica em 2019 foi a imagem de M87*, buraco negro supermassivo central da galáxia Messier 87. A partir da observação da colaboração Event Horizon Telescope, fomos capazes de ver um buraco negro. Na verdade, a famosa imagem mostra-nos a sombra de M87*. Neste artigo, será introduzido o conceito de sombra de um buraco negro e indicada a sua importância para pesquisas nas áreas de gravitação e cosmologia.
In this work, we present black hole solutions with a cosmological constant in bumblebee gravity, ... more In this work, we present black hole solutions with a cosmological constant in bumblebee gravity, which provides a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. From the gravitational point of view, such solutions are spherically symmetric black holes with an effective cosmological constant and are supported by an anisotropic energy-momentum tensor, conceived of as the manifestation of the bumblebee field in the spacetime geometry. Then we calculate the shadow angular radius for the proposed black hole solution with a positive effective cosmological constant. In particular, our results are the very first relation between the bumblebee field and the shadow angular size.
A constraint on the tidal charge generated within a brane world is shown. Using the shadow of a r... more A constraint on the tidal charge generated within a brane world is shown. Using the shadow of a rotating black hole in a brane context in order to describe the M87* parameters recently announced by the Event Horizon Telescope Collaboration, the deviation from circularity of the reported shadow produces an upper bound on the bulk's nonlocal effect, which is conceived of as a tidal charge in the four-dimensional brane induced by the five-dimensional bulk. Therefore, a deviation from circularity 10% leads to an upper bound on the tidal charge 0.004M 2 .
An upper bound on the parameter that provides a generalized uncertainty principle (GUP) is obtai... more An upper bound on the parameter that provides a generalized uncertainty principle (GUP) is obtained from the black hole shadow. With the aid of a recent constraint between regular black holes and the GUP parameter, it is indicated a relation between this parameter and the deviation from circularity of the black hole shadow. In the case of the recent announcement of the M87* results from the Event Horizon Telescope collaboration, a deviation from circularity $\lesssim 10\%$ imposes a GUP parameter $\beta_0 <10^{90}$.
We consider the stationary spherical accretion process of perfect fluids onto a class of spherica... more We consider the stationary spherical accretion process of perfect fluids onto a class of spherically symmetric regular black holes corresponding to quantum-corrected Schwarzschild spacetimes. We show that the accretion rates can differ from the Schwarzschild case, suggesting that the de Sitter core inside these regular black holes, which indeed precludes the central singularity, can act for some cases as a sort of antigravitational source, decreasing the fluid's radial infall velocity in the accretion process, and for others as a gravitational enhancer, increasing the fluid flow into the black hole horizon. Our analysis and results can be extended and applied also to the problem of black hole evaporation in cosmological scenarios with phantom fluids. In particular, we show that the mass of typical regular black holes could be used to constrain turnaround events in cyclic cosmologies.
In spite of successful tests, the standard cosmological model, the ΛCDM model, possesses the most... more In spite of successful tests, the standard cosmological model, the ΛCDM model, possesses the most problematic concept: the initial singularity, also known as the big bang. In this paper—by adopting the Kantian difference between to think of an object and to cognize an object—it is proposed a degree of scientificity using fuzzy sets. Thus, the notion of initial singularity will not be conceived of as a scientific issue because it does not belong to the fuzzy set of what is known. Indeed, the problematic concept of singularity is some sort of what Kant called the noumenon, but science, on the other hand, is constructed in the phenomenon. By applying the fuzzy degree of scientificity in cosmological models, one concludes that cosmologies with a contraction phase before the current expansion phase are potentially more scientific than the standard model. At the end of this article, it is shown that Kant's first antinomy of pure reason indicates a limit to our cosmological models.
It is shown that an aspect of the process of individuation may be thought of as a fuzzy set. The ... more It is shown that an aspect of the process of individuation may be thought of as a fuzzy set. The process of individuation has been interpreted as a two-valued problem in the history of philosophy. In this work, I intend to show that such a process in its psychosocial aspect is better understood in terms of a fuzzy set, characterized by a continuum membership function. According to this perspective, species and their members present different degrees of individuation. Such degrees are measured from the membership function of the psychosocial process of individuation. Thus, a social analysis is suggested by using this approach in human societies.
It is shown that a notion of natural place is possible within modern physics. For Aristotle, the ... more It is shown that a notion of natural place is possible within modern physics. For Aristotle, the elements—the primary components of the world—follow to their natural places in the absence of forces. On the other hand, in general relativity, the so-called Carter-Penrose diagrams offer a notion of end for objects along the geodesics. Then, the notion of natural place in Aristotelian physics has an analog in the notion of conformal infinities in general relativity.
Bardeen regular black hole is commonly considered as a solution of general relativity coupled to ... more Bardeen regular black hole is commonly considered as a solution of general relativity coupled to a nonlinear electrodynamics. In this paper, it is shown that the Bardeen solution may be interpreted as a quantum-corrected Schwarzschild black hole. This new interpretation is obtained by means of a generalized uncertainty principle applied to the Hawking temperature. Moreover, using the regular black hole of Bardeen, it is possible to evaluate the quantum gravity parameter of the generalized uncertainty principle or, assuming the recent upper bounds for such a parameter, to verify an enormous discrepancy between a cosmological constant and that measured by recent cosmological observations (∼ 10^120).
In this article, we present a study on thermodynamics of a class of regular black holes. Such a c... more In this article, we present a study on thermodynamics of a class of regular black holes. Such a class includes Bardeen and Hayward regular black holes. We obtained thermodynamic quantities like Hawking temperature, entropy and heat capacity for the entire class. As part of an effort to indicate some physical observable to distinguish regular black holes from singular black holes, we suggest that regular black holes are colder than singular black holes. Besides, contrary to Schwarzschild black hole, that class of regular black holes may be thermodynamically stable. From a generalized uncertainty principle, we also obtained the quantum-corrected thermodynamics for the studied class. Such quantum corrections provide a logarithmic term for the quantum-corrected entropy.
In this work, the interior spacetime of stars is built in a Lorentz symmetry breaking model calle... more In this work, the interior spacetime of stars is built in a Lorentz symmetry breaking model called bumblebee gravity. Firstly, we calculated the modified Tolman-Oppenheimer-Volkoff equation in this context of modified gravity. Then we show that the bumblebee field, responsible for the symmetry breaking, increases the star mass-radius relation when it assumes its vacuum expectation value. When compared to the general relativity mass-radius relation, a Lorentz symmetry breaking context, like the bumblebee gravity, could provide more massive stars, surpassing the 2.5M⊙ limit as the interior of the star is described by quark matter with the MIT bag model.
Monthly Notices of the Royal Astronomical Society, 2023
The co-varying physical couplings (CPC) framework states that physical parameters like the speed ... more The co-varying physical couplings (CPC) framework states that physical parameters like the speed of light in vacuum c, the Newtonian constant G, and the cosmological constant Λ could indeed vary with the spacetime coordinates x µ. Here, we assume a temporal variation, that is, c(t), G(t) and Λ(t). We show that the McVittie spacetime, a black hole in an expanding universe, is a solution of the CPC framework providing naturally an important parameter of the model. Then, we calculate the shadow angular radius of this black hole at cosmological distances. A black hole shadow in the CPC context could be either larger or smaller than the same shadow in the standard cosmology. It depends on how the set {c, G, Λ} varies with time or with the cosmic expansion.
There have been three geometrizations in history. The first one is historically due to the Pythag... more There have been three geometrizations in history. The first one is historically due to the Pythagorean school and Plato, the second one comes from Galileo, Kepler, Descartes and Newton, and the third is Einstein's geometrization of nature. The term geometrization of nature means the conception according to which nature (with its different meanings) is massively described by using geometry. In this article, I focus on the third geometrization, in which the black hole shadow phenomenon provides an interesting statement about the level of geometrization achieved by the theory of general relativity. With the black hole shadow described by the Einsteinian theory, the geometrical interpretation of nature relates shape to dynamics or, more specifically, the shadow silhouette to the angular momentum, regardless the matter content inside the black hole. As a consequence, spacetime symmetry could play the role of the formal cause in black hole physics.
Following a recent approach in which the gravitational field equations in curved spacetimes were ... more Following a recent approach in which the gravitational field equations in curved spacetimes were presented in the Bopp–Podolsky electrodynamics, we obtained an approximate and spherically symmetric wormhole solution in this context. The calculations were carried out up to the linear approximation in both the spacetime geometry and the radial electric field. The solution presents a new parameter that comes from the Lagrangian of the model. Such a parameter was constrained by using the shadow radius of Sagittarius A*, recently revealed by the Event Horizon Telescope
Collaboration. Remarkably, the wormhole presented here is viable when its shadow is compared to the Sagittarius A* shadow.
Kasner cosmology is a vacuum and anisotropically expanding spacetime in the general relativity co... more Kasner cosmology is a vacuum and anisotropically expanding spacetime in the general relativity context. In this work, such a cosmological model is studied in another context, the bumblebee model, where the Lorentz symmetry is spontaneously broken. By using the bumblebee context it is possible to justify the anisotropic feature of the Kasner cosmology. Thus, the origin of the anisotropy in this cosmological model could be in the Lorentz symmetry breaking. Lastly, an application in the pre-inflationary cosmology is suggested.
The theory of regularity is a philosophical perspective in which laws of nature are just descript... more The theory of regularity is a philosophical perspective in which laws of nature are just descriptions, that is to say, laws of nature do not govern the world. Moreover, according to the theory of regularity, the number of laws of nature might be infinite, thus any attempt towards the theory of everything is doomed. Here I propose a special or restricted theory of regularity. The main difference as to the well-known version of that theory is both the range of validity and the scale of the laws of nature. Laws of nature ought to be considered just inside the observable universe and within certain energy and length scales. Even so I apply the theory of regularity to the multiverse scenario. As a consequence, the special theory of regularity supports only two types of multiverses by comparison with our world: those ones with a different sequence of unique events and different laws of nature and those ones with the same sequence of unique events and the same laws of nature instanced by the unique events. The latter case is some sort of eternal recurrence or a parallel eternal recurrence.
An effect of the Lorentz symmetry breaking is pointed out in the cosmological context. Using a Bi... more An effect of the Lorentz symmetry breaking is pointed out in the cosmological context. Using a Bianchi I geometry coupled to the Kalb-Ramond field, a consequence of the Lorentz symmetry violation is indicated by a different rate of expansion in a given spatial direction. This article focuses on the coupling constant ξ1, which generates, from the Kalb-Ramond field, all three coefficients that give rise to the Lorentz violation in the gravity sector of the minimal Standard Model Extension. The coupling constant ξ1 increases the rate of expansion of the universe in a given direction during a dark energy era. As a consequence, a range of validity of that coupling constant is also obtained.
Nietzsche colocou-se como um antípoda a Platão. Mas em questões cosmológicas, o eterno retorno ni... more Nietzsche colocou-se como um antípoda a Platão. Mas em questões cosmológicas, o eterno retorno nietzschiano tem também alguns pontos em comum à cosmologia platônica descrita no Timeu. A finitude espacial, a ciclicidade cósmica e a ética cosmológica dizem respeito às semelhanças, já a infinitude temporal, a teleologia e a necessidade afastam os filósofos. Então, neste trabalho, aponto proximidades e afastamentos entre os dois filósofos em questões cosmológicas, além de sugerir alguma atualidade de suas concepções em relação à nossa ciência. Como veremos, a relação entre ética e cosmologia ainda se mostra atual.
Following a recent approach, complete and analytic solutions (brane and bulk) of regular black ho... more Following a recent approach, complete and analytic solutions (brane and bulk) of regular black holes are shown in a brane context. The metrics are regular both on the four-dimensional brane and in the five-dimensional bulk. Like many brane world scenarios, the bulk spacetime is asymptotically anti-de Sitter. On the other hand, a de Sitter core on the brane avoids the singularity inside the event horizon, providing then well-known regular black holes on the brane. From the bulk perspective, the regular black holes are five-dimensional objects, with the event horizon extending to the extra dimension, but the de Sitter core is entirely on the four-dimensional brane.
Journal of Cosmology and Astroparticle Physics, 2021
In this work, a bumblebee field is adopted in order to generate cosmological anisotropies. For th... more In this work, a bumblebee field is adopted in order to generate cosmological anisotropies. For that purpose, we assume a Bianchi I cosmology, as the background geometry, and a bumblebee field coupled to it. Bumblebee models are examples of a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. When coupled to the Bianchi I geometry, which is not in agreement with a cosmological principle, the bumblebee field plays the role of a source of anisotropies and produces a preferred axis. Thus, a fraction of the cosmic anisotropies would come from the Lorentz symmetry violation. In the last part of the article, we try to assume an upper bound on the bumblebee field using the quadrupole and octopole moments of the cosmic microwave background radiation.
A mais comentada imagem científica em 2019 foi a imagem de M87*, buraco negro supermassivo centra... more A mais comentada imagem científica em 2019 foi a imagem de M87*, buraco negro supermassivo central da galáxia Messier 87. A partir da observação da colaboração Event Horizon Telescope, fomos capazes de ver um buraco negro. Na verdade, a famosa imagem mostra-nos a sombra de M87*. Neste artigo, será introduzido o conceito de sombra de um buraco negro e indicada a sua importância para pesquisas nas áreas de gravitação e cosmologia.
In this work, we present black hole solutions with a cosmological constant in bumblebee gravity, ... more In this work, we present black hole solutions with a cosmological constant in bumblebee gravity, which provides a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. From the gravitational point of view, such solutions are spherically symmetric black holes with an effective cosmological constant and are supported by an anisotropic energy-momentum tensor, conceived of as the manifestation of the bumblebee field in the spacetime geometry. Then we calculate the shadow angular radius for the proposed black hole solution with a positive effective cosmological constant. In particular, our results are the very first relation between the bumblebee field and the shadow angular size.
A constraint on the tidal charge generated within a brane world is shown. Using the shadow of a r... more A constraint on the tidal charge generated within a brane world is shown. Using the shadow of a rotating black hole in a brane context in order to describe the M87* parameters recently announced by the Event Horizon Telescope Collaboration, the deviation from circularity of the reported shadow produces an upper bound on the bulk's nonlocal effect, which is conceived of as a tidal charge in the four-dimensional brane induced by the five-dimensional bulk. Therefore, a deviation from circularity 10% leads to an upper bound on the tidal charge 0.004M 2 .
An upper bound on the parameter that provides a generalized uncertainty principle (GUP) is obtai... more An upper bound on the parameter that provides a generalized uncertainty principle (GUP) is obtained from the black hole shadow. With the aid of a recent constraint between regular black holes and the GUP parameter, it is indicated a relation between this parameter and the deviation from circularity of the black hole shadow. In the case of the recent announcement of the M87* results from the Event Horizon Telescope collaboration, a deviation from circularity $\lesssim 10\%$ imposes a GUP parameter $\beta_0 <10^{90}$.
We consider the stationary spherical accretion process of perfect fluids onto a class of spherica... more We consider the stationary spherical accretion process of perfect fluids onto a class of spherically symmetric regular black holes corresponding to quantum-corrected Schwarzschild spacetimes. We show that the accretion rates can differ from the Schwarzschild case, suggesting that the de Sitter core inside these regular black holes, which indeed precludes the central singularity, can act for some cases as a sort of antigravitational source, decreasing the fluid's radial infall velocity in the accretion process, and for others as a gravitational enhancer, increasing the fluid flow into the black hole horizon. Our analysis and results can be extended and applied also to the problem of black hole evaporation in cosmological scenarios with phantom fluids. In particular, we show that the mass of typical regular black holes could be used to constrain turnaround events in cyclic cosmologies.
In spite of successful tests, the standard cosmological model, the ΛCDM model, possesses the most... more In spite of successful tests, the standard cosmological model, the ΛCDM model, possesses the most problematic concept: the initial singularity, also known as the big bang. In this paper—by adopting the Kantian difference between to think of an object and to cognize an object—it is proposed a degree of scientificity using fuzzy sets. Thus, the notion of initial singularity will not be conceived of as a scientific issue because it does not belong to the fuzzy set of what is known. Indeed, the problematic concept of singularity is some sort of what Kant called the noumenon, but science, on the other hand, is constructed in the phenomenon. By applying the fuzzy degree of scientificity in cosmological models, one concludes that cosmologies with a contraction phase before the current expansion phase are potentially more scientific than the standard model. At the end of this article, it is shown that Kant's first antinomy of pure reason indicates a limit to our cosmological models.
It is shown that an aspect of the process of individuation may be thought of as a fuzzy set. The ... more It is shown that an aspect of the process of individuation may be thought of as a fuzzy set. The process of individuation has been interpreted as a two-valued problem in the history of philosophy. In this work, I intend to show that such a process in its psychosocial aspect is better understood in terms of a fuzzy set, characterized by a continuum membership function. According to this perspective, species and their members present different degrees of individuation. Such degrees are measured from the membership function of the psychosocial process of individuation. Thus, a social analysis is suggested by using this approach in human societies.
It is shown that a notion of natural place is possible within modern physics. For Aristotle, the ... more It is shown that a notion of natural place is possible within modern physics. For Aristotle, the elements—the primary components of the world—follow to their natural places in the absence of forces. On the other hand, in general relativity, the so-called Carter-Penrose diagrams offer a notion of end for objects along the geodesics. Then, the notion of natural place in Aristotelian physics has an analog in the notion of conformal infinities in general relativity.
Bardeen regular black hole is commonly considered as a solution of general relativity coupled to ... more Bardeen regular black hole is commonly considered as a solution of general relativity coupled to a nonlinear electrodynamics. In this paper, it is shown that the Bardeen solution may be interpreted as a quantum-corrected Schwarzschild black hole. This new interpretation is obtained by means of a generalized uncertainty principle applied to the Hawking temperature. Moreover, using the regular black hole of Bardeen, it is possible to evaluate the quantum gravity parameter of the generalized uncertainty principle or, assuming the recent upper bounds for such a parameter, to verify an enormous discrepancy between a cosmological constant and that measured by recent cosmological observations (∼ 10^120).
In this article, we present a study on thermodynamics of a class of regular black holes. Such a c... more In this article, we present a study on thermodynamics of a class of regular black holes. Such a class includes Bardeen and Hayward regular black holes. We obtained thermodynamic quantities like Hawking temperature, entropy and heat capacity for the entire class. As part of an effort to indicate some physical observable to distinguish regular black holes from singular black holes, we suggest that regular black holes are colder than singular black holes. Besides, contrary to Schwarzschild black hole, that class of regular black holes may be thermodynamically stable. From a generalized uncertainty principle, we also obtained the quantum-corrected thermodynamics for the studied class. Such quantum corrections provide a logarithmic term for the quantum-corrected entropy.
Em 586 notas ou seções, temas como ciência, filosofia, universidade, internet e Brasil são discut... more Em 586 notas ou seções, temas como ciência, filosofia, universidade, internet e Brasil são discutidos com seriedade e humor. Da morte de Deus da filosofia nietzschiana à cosmologia eterna einsteiniana, sem um big bang, do mundo quântico aos buracos negros, passando pela modernidade digital e o esvaziamento dos valores, as notas caminham do cósmico ao humano e do sublime ao vulgar. O livro é, no final das contas, sem álgebra alguma, um movimento do "universal" ao particular vivido pelo autor nesta terra chamada Brasil.
No livro, o mito do Timeu de Platão é usado para evidenciar a inerente atividade artística humana... more No livro, o mito do Timeu de Platão é usado para evidenciar a inerente atividade artística humana. O Demiurgo, que criou o cosmo na obra platônica, não é apenas um. São inúmeros os demiurgos e as suas demiurgias. Em especial, na ciência de hoje são encontradas demiurgias avançadas, ricas e influentes. Um caminho é percorrido para mostrar ao leitor as nossas demiurgias científicas: do microcosmo ao macrocosmo. Ou seja, da mecânica quântica à teoria da relatividade geral ou da física das partículas à cosmologia, será mostrado que “o mundo” foi e ainda é criado por demiurgos. Com as ferramentas que Nietzsche nos deixou, veremos que as demiurgias, com maior atenção dada às demiurgias científicas e tecnológicas no presente livro, partem do caos para gerar não apenas um, mas inúmeros mundos.
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Papers by Juliano C S Neves
Collaboration. Remarkably, the wormhole presented here is viable when its shadow is compared to the Sagittarius A* shadow.
nature ought to be considered just inside the observable universe and within certain energy and length scales. Even so I apply the theory of regularity to the multiverse scenario. As a consequence, the special theory of regularity supports only two types of multiverses by comparison with our world: those ones with a different sequence of unique events and different laws of nature and those ones with the same sequence of unique events and the same laws of nature instanced by the unique events. The latter case is some sort of eternal recurrence or a parallel eternal recurrence.
Collaboration. Remarkably, the wormhole presented here is viable when its shadow is compared to the Sagittarius A* shadow.
nature ought to be considered just inside the observable universe and within certain energy and length scales. Even so I apply the theory of regularity to the multiverse scenario. As a consequence, the special theory of regularity supports only two types of multiverses by comparison with our world: those ones with a different sequence of unique events and different laws of nature and those ones with the same sequence of unique events and the same laws of nature instanced by the unique events. The latter case is some sort of eternal recurrence or a parallel eternal recurrence.