Regular black holes in f(G) gravity de S. Silva, Marcos V.; Rodrigues, Manuel E.
The European physical journal. C, Particles and fields,
08/2018, Volume:
78, Issue:
8
Journal Article
Peer reviewed
Open access
In this work, we study the possibility of generalizing solutions of regular black holes with an electric charge, constructed in general relativity, for the
f
(
G
) theory, where
G
is the Gauss–Bonnet ...invariant. This type of solution arises due to the coupling between gravitational theory and nonlinear electrodynamics. We construct the formalism in terms of a mass function and it results in different gravitational and electromagnetic theories for which mass function. The electric field of these solutions are always regular and the strong energy condition is violated in some region inside the event horizon. For some solutions, we get an analytical form for the
f
(
G
) function. Imposing the limit of some constant going to zero in the
f
(
G
) function we recovered the linear case, making the general relativity a particular case.
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We develop a number of novel "black-bounce" spacetimes. These are specific regular black holes where the area radius always remains nonzero, thereby leading to a "throat" that is either timelike ...(corresponding to a traversable wormhole), spacelike (corresponding to a "bounce" into a future universe), or null (corresponding to a "one-way wormhole"). We first perform a general analysis of the regularity conditions for such a spacetime and then consider a number of specific examples. The examples are constructed using a mass function similar to that of Fan-Wang and fall into several particular cases, such as the original Simpson-Visser model, a Bardeen-type model, and other generalizations thereof. We analyze the regularity, energy conditions, and causal structure of these models. The main results are several new geometries, more complex than before, with two or more horizons, with the possibility of an extremal case. We derive a general theorem regarding static spacetime regularity and another general theorem regarding (non)satisfaction of the classical energy conditions.
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Regular black holes in Rainbow Gravity Junior, Ednaldo L.B.; Rodrigues, Manuel E.; de S. Silva, Marcos V.
Nuclear physics. B,
December 2020, 2020-12-00, Volume:
961
Journal Article
Peer reviewed
Open access
In this work, we consider that in energy scales near to the Planck energy, the geometry, mass, speed of light, the Newtonian constant of gravitation and matter fields will depend on the energy. This ...type of theory is known as Rainbow Gravity. We coupled the nonlinear electrodynamics to the Rainbow Gravity, defining a new mass function M(r,ϵ), such that we may formulate new classes of spherically symmetric regular black hole solutions, where the curvature invariants are well-behaved in all spacetime. The main differences between the General Relativity and our results in the Rainbow gravity are: a) The intensity of the electric field is inversely proportional to the energy scale. The higher the energy scale, the lower the electric field intensity; b) the region where the strong energy condition (SEC) is violated decreases as the energy scale increases.
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Orbits Around a Black Bounce Spacetime de S. Silva, Marcos V.; Rodrigues, Manuel E.
International journal of theoretical physics,
04/2024, Volume:
63, Issue:
4
Journal Article
Peer reviewed
In this work, the trajectories of particles around a black bounce spacetime are considered, with the Simpson-Visser model serving as an example. Trajectories for massless and massive particles are ...obtained through the study of null and time-like geodesics. As the Simpson-Visser solution is derived via the Einstein equations for a source involving nonlinear electrodynamics and a scalar field, photon trajectories are investigated by considering an effective metric in which photons follow null geodesics. The stability of circular orbits is analyzed by examining the behavior of maxima and minima of the effective potential associated with geodesics. It is also studied what type of geodesic photons follow when the usual metric is considered instead of the effective one. The main focus of this work is to obtain corrections to the trajectories of photons when considering that the solution arises from nonlinear electrodynamics.
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Key message
We propose the application of enviromics to breeding practice, by which the similarity among sites assessed on an “omics” scale of environmental attributes drives the prediction of ...unobserved genotype performances.
Genotype by environment interaction (GEI) studies in plant breeding have focused mainly on estimating genetic parameters over a limited number of experimental trials. However, recent geographic information system (GIS) techniques have opened new frontiers for better understanding and dealing with GEI. These advances allow increasing selection accuracy across all sites of interest, including those where experimental trials have not yet been deployed. Here, we introduce the term enviromics, within an envirotypic-assisted breeding framework. In summary, likewise genotypes at DNA markers, any particular site is characterized by a set of “envirotypes” at multiple “enviromic” markers corresponding to environmental variables that may interact with the genetic background, thus providing informative breeding re-rankings for optimized decisions over different environments. Based on simulated data, we illustrate an index-based enviromics method (the “GIS–GEI”) which, due to its higher granular resolution than standard methods, allows for: (1) accurate matching of sites to their most appropriate genotypes; (2) better definition of breeding areas that have high genetic correlation to ensure selection gains across environments; and (3) efficient determination of the best sites to carry out experiments for further analyses. Environmental scenarios can also be optimized for productivity improvement and genetic resources management, especially in the current outlook of dynamic climate change. Envirotyping provides a new class of markers for genetic studies, which are fairly inexpensive, increasingly available and transferable across species. We envision a promising future for the integration of enviromics approaches into plant breeding when coupled with next-generation genotyping/phenotyping and powerful statistical modeling of genetic diversity.
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Abstract
In this article, we test the possibility of building new black-bounce spacetimes with changes in the area in the context of general relativity in four dimensions. These new metrics can ...present extra structures, such as anti-throats. We see two regions where the area goes to infinity, and, depending on the model, one of these regions presents curvature singularities. Regular metrics can be extended to negative values of the radial coordinate and have a symmetrical structure, whereas some singular cases cannot be extended and have no symmetrical structure. The energy conditions are analyzed, and, for some cases, at least one of the inequalities in the null energy condition is not respected. We also presented models that satisfied the null energy condition outside the event horizon. The event horizon hides the throats of these models.
In this work, we study the existence of regular black hole solutions with multihorizons in general relativity and in some alternative theories of gravity. We consider the coupling between the ...gravitational theory and nonlinear electrodynamics. The coupling generates modifications in the electromagnetic sector. The main objective of this paper is to generalize the solutions already known from general relativity to f(G) theory. First, we correct some misprints of Odintsov and Nojiri's work in order to introduce the formalism that is used in f(G) gravity. In order to satisfy all field equations, the method to find solutions to alternative theories generates different f(R) and f(G) functions for each solution, where only the nonlinear term of f(G) contributes to the field equations. We also analyze the energy conditions, since it is expected that some must be violated to find regular black holes, and using an auxiliary field, we analyze the nonlinearity of the electromagnetic theory.
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10.
Multicomponent Reactions (MCRs) with o‐Quinone Methides Martins, Maria Tereza M.; Dias, Flaviana Rodrigues F.; Moraes, Raphael Silva M. ...
Chemical record,
March 2022, 2022-Mar, 2022-03-00, 20220301, Volume:
22, Issue:
3
Journal Article
Peer reviewed
This article presents a comprehensive overview of multicomponent reactions (MCRs) that proceed via ortho‐quinone methide intermediates (o‐QM) generated in the reaction medium. Examples of ...applications involving these highly reactive intermediates in organic synthesis and biological processes (e. g., biosynthetic pathways, prodrug cleavage and electrophilic capture of biological nucleophiles) are also described. QMs are often generated by eliminative processes of phenol derivatives or by photochemical reactions, including reversible generation in photochromic substances. This class of compounds can undergo various reaction types, including nucleophilic attack at the methide carbon, with subsequent rearomatization, and react with electron‐rich dienophiles in inverse‐electron demand hetero‐Diels‐Alder reactions. Its versatile reactivity has been explored in the context of cascade reactions for the construction of several classes of substances, including complex natural products.
This article presents a comprehensive overview of multicomponent reactions (MCRs) that proceed via ortho‐quinone methide intermediates (o‐QM) generated in the reaction medium. Examples of applications involving these highly reactive intermediates in organic synthesis and biological processes (e. g., biosynthetic pathways, prodrug cleavage and electrophilic capture of biological nucleophiles) are also described.
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