Article
Physics, Multidisciplinary
C. R. Muniz, R. V. Maluf
Summary: This paper investigates generalized Ellis-Bronikov (E-B) traversable wormholes in f (R) extended gravity, assuming the support of anisotropic dark matter (DM) and discussing different DM models and the feasibility of the wormhole-dark matter system.
Article
Astronomy & Astrophysics
Bruno J. Barros, Alvaro de la Cruz-Dombriz, Francisco S. N. Lobo
Summary: In this study, novel analytical solutions for static and spherically symmetric wormhole geometries threaded by an anisotropic distribution of matter conformally coupled to a scalar ghost field are presented. The dynamics of the scalar field and matter throughout the wormhole, as well as the role played by the nonminimal coupling, are explored. Furthermore, coupled ghosts in the presence of a scalar potential are considered, and the traversability conditions within such geometrical scheme are analyzed.
Article
Physics, Particles & Fields
Joao Luis Rosa, Paul Martin Kull
Summary: In this study, we analyze traversable wormhole solutions in the linear form of f (R, T) = R + lambda T gravity, satisfying the energy conditions. Through a comprehensive analysis of the free parameters of the wormhole model, we obtain the bounds on these parameters for which the energy conditions are satisfied and provide two explicit solutions. Even if some of these bounds are violated, physically relevant wormhole solutions can still be found by matching with an exterior vacuum spacetime.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Jan de Boer, Viktor Jahnke, Keun-Young Kim, Juan F. Pedraza
Summary: We construct worldsheet traversable wormholes by considering the effects of a double-trace deformation, coupling the endpoints of an open string in AdS space. The operator deforming the theory is irrelevant and makes the boundaries bend inward toward the IR. This effect renders the teleportation protocol more efficient and facilitates the transfer of information between the members of the dual Bell pair. We compare our results with those obtained with the standard double-trace deformation introduced by Gao, Jafferis and Wall.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Astronomy & Astrophysics
Abdelghani Errehymy, Sudan Hansraj, S. K. Maurya, Chevarra Hansraj, Mohammed Daoud
Summary: In this paper, the authors study spherically symmetric traversable wormholes in the torsion and matter coupling gravity formalism. They thoroughly investigate the field equations for wormhole solutions and find the violation of null energy conditions in the throat vicinity. By considering specific choices for matter content, they present an intriguing new class of solutions for static and spherically symmetric wormholes that obey the necessary metric conditions.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
Joao Luis Rosa, Nailya Ganiyeva, Francisco S. N. Lobo
Summary: In this work, we analyze traversable wormhole spacetimes within the framework of energy-momentum squared gravity. We show that a wide variety of wormhole solutions satisfying all energy conditions exist without the need for fine-tuning of model parameters. The solutions are obtained through an analytical recursive algorithm, and matching conditions with an external vacuum are derived. By matching the interior wormhole spacetime with the Schwarzschild solution, we obtain localized static and spherically symmetric wormhole solutions that satisfy all energy conditions for the entire spacetime range.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
A. Bakopoulos, C. Charmousis, P. Kanti
Summary: In this study, we construct a large class of explicit, asymptotically flat and regular wormhole solutions in higher order scalar tensor theories. These solutions are obtained through a general disformal transformation of a seed black hole solution. The wormholes are parametrized by their ADM mass and two coupling constants of the theory, one related to their higher dimensional Lovelock origin and one to the disformal transformation itself.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Mathematical
Archana Dixit, Chanchal Chawla, Anirudh Pradhan
Summary: A new form of logarithmic shape function is proposed for the linear f(R,T) gravity in wormhole geometry, satisfying the necessary conditions for a traversable and asymptotically flat wormhole. The analysis of obtained wormhole solutions reveals the existence of exotic and non-exotic matter representing different values of lambda. Additionally, it is confirmed that exotic matter exists in wormhole geometry for the general relativity case with lambda = 0. Further examination of radial state parameter, tangential state parameter, and anisotropy parameter behavior is presented for varied lambda values between -100 and 100.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2021)
Article
Physics, Multidisciplinary
Salvatore Capozziello, Orlando Luongo, Lorenza Mauro
Summary: Exact traversable wormhole solutions are derived in the f(R) gravity framework with stable conditions over the geometric fluid entering the throat. Two possible approaches for the shape function b(r)/r are proposed, leading to stable solutions with small deviations from general relativity. Suitable bounds over the parameters of the model are obtained for the discussed cases.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Astronomy & Astrophysics
Erik Jimenez-Vazquez, Miguel Alcubierre
Summary: We study the critical gravitational collapse of a massless scalar field nonminimally coupled to gravity and determine the values of critical amplitude, critical exponent, and echoing exponent. We find that the behavior is similar to that of a minimally coupled scalar field for small coupling, but becomes more violent and rich in high coupling. A special slicing condition is introduced to avoid gauge pathologies in the strong-coupling regime.
Article
Astronomy & Astrophysics
Parbati Sahoo, P. H. R. S. Moraes, Marcelo M. Lapola, P. K. Sahoo
Summary: The paper proposes modeling traversable wormholes within an alternative gravity theory and discusses the wormhole material content by applying energy conditions to them.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Astronomy & Astrophysics
Kishan Sankharva, Shiv Sethi
Summary: In this paper, we consider a nonminimally coupled scalar field as a candidate for cold dark matter and compare it with minimally coupled scalar fields. For the nonminimally coupled field, the energy density behaves as radiation in the early universe and is constrained by a coupling constant. Isocurvature modes are also considered in our analysis.
Article
Physics, Multidisciplinary
Rabia Saleem, M. Israr Aslam
Summary: In this paper, we investigate the existence of traversable wormholes in the framework of f(R,T) gravity with non-exotic matter and the hypothetical condition of stability inside the wormhole throat. By choosing suitable shape functions and considering the bounds on model parameters, we find the necessary conditions for stable solutions.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Physics, Particles & Fields
Oleksii Sokoliuk, Alexander Baransky
Summary: We study Morris-Thorne static traversable wormhole solutions in different modified theories of gravity and derive suitable shape functions by numerically solving the Einstein field equations. The stability of Morris-Thorne wormholes and energy conditions are analyzed, and general formulas for the extra force in MTOV due to the non-conserved stress-energy tensor are derived.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Mathematical
Nisha Godani
Summary: This paper investigates traversable wormhole solutions in a specific gravitational theory and explores the parameter range and effect of charge on these solutions.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2021)
Article
Astronomy & Astrophysics
C. Gomes, O. Bertolami
Summary: In this study, we restrict the viable models of Horndeski gravity, formulated as the equivalent Generalised Galileon version, using the Witten positive energy theorem. The analysis reveals that the free function G(3)(phi, X) in the Lagrangian is solely dependent on the scalar field, G(3)(phi), and establishes relationships among the free functions. Additionally, stability criteria such as gravity attractiveness and Dolgov-Kawasacki instability are examined, and cosmological applications are discussed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Ricardo Z. Ferreira, David Marsh, Eike Muller
Summary: ALPs with feeble couplings to electrons cannot make up dark matter as their lifetimes are shorter than the age of the Universe. Constraints from x-ray and γ-ray astronomy exceed current laboratory limits on ALPs in the 6 keV to 1 MeV mass range.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Ricardo Z. Ferreira, Alessio Notari, Oriol Pujolas, Fabrizio Rompineve
Summary: Heavy QCD axion models are crucial for solving the strong CP problem, and can be probed through measurements of gravitational wave signals and electric dipole moments. Future observatories are expected to further explore this model.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Orfeu Bertolami, Maria Margarida Lima, Filipe C. Mena
Summary: The existence of magnetic fields in the universe is observed at all scales, but their origin remains unknown. In the context of non-minimal coupling gravity theory, it is found that under certain conditions, the generated magnetic fields during inflation can be compatible with large-scale observations.
GENERAL RELATIVITY AND GRAVITATION
(2022)
Article
Astronomy & Astrophysics
Orfeu Bertolami, Frederico Francisco
Summary: A classification scheme for rocky planets is proposed based on the Landau-Ginzburg Theory, and the impact of Earth's transition from Holocene to Anthropocene on other planets is discussed. The similarities between Earth and Venus are highlighted, suggesting the possibility of a hot-house Earth scenario resulting from the Anthropocene transition.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Orfeu Bertolami, Paulo M. Sa
Summary: Multi-field cold inflation models are usually at odds with the swampland conjectures in string theory, but can be reconciled in the strong dissipative regime of warm inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Ricardo Z. Ferreira, M. C. David Marsh, Eike Muller
Summary: We demonstrate that the one-loop effective coupling of axionlike particles (ALPs) to photons is process dependent in theories where they are coupled to electrons. This has significant implications for the physics of massive ALPs in hot and dense environments, such as supernovae.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
A. E. Bernardini, O. Bertolami
Summary: The existence of time crystals, which explains the unexpected non-stationary behavior of quantum observables in the ground state, requires a spontaneous breakdown of the continuous time translation symmetry. This study argues that such effects emerge from the noncommutativity of position and/or momentum and presents a predictive analysis of the two-dimensional noncommutative quantum harmonic oscillator using the Weyl-Wigner-Groenewold-Moyal framework. The analysis shows how the phase-space noncommutativity drives the amplitude of periodic oscillations identified as time crystals.
Article
Physics, Multidisciplinary
A. E. Bernardini, O. Bertolami
Summary: Quantum mechanics plays a crucial role in modeling competitive ecological systems and self-organizing structures. The dynamics of prey-predator competition in phase space can be described within the framework of Weyl-Wigner quantum mechanics, with quantum states convoluted by statistical gaussian ensembles. Quantum modifications on the equilibrium and stability of the prey-predator dynamics can be identified through the Wigner current fluxes obtained from an onset Hamiltonian background. Additionally, emergent topological quantum domains affect the stability properties of gaussian ensembles localized around the equilibrium point, leading to extinction and revival scenarios or perpetual coexistence of prey and predator agents.
FOUNDATIONS OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
Orfeu Bertolami
Summary: The vacuum can have two different phases, one dominated by non-relativistic matter and the other being a de Sitter phase, according to the Chaplygin equation or its generalised version. Particle production during the matter-like phase can generate entanglement entropy and the interactions provide the environment for gravitational quantum features to become classical. In the de Sitter phase, the cosmological constant can be suppressed by inflation.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Physics, Fluids & Plasmas
A. E. Bernardini, O. Bertolami
Summary: This paper investigates the nonequilibrium and instability features of prey-predator-like systems associated with topological quantum domains emerging from a quantum phase-space description. By reporting the generalized Wigner flow for one-dimensional Hamiltonian systems, the prey-predator dynamics driven by Lotka-Volterra equations is mapped onto the Heisenberg-Weyl noncommutative algebra. The result shows that the equilibrium and stability parameters for the prey-predator-like dynamics are affected by quantum distortions, quantified in terms of Wigner currents and Gaussian ensemble parameters.
Article
Astronomy & Astrophysics
Orfeu Bertolami, Claudio Gomes, Paulo M. Sa
Summary: In this paper, we investigate whether inflationary solutions driven by a single scalar field can be consistent with the swampland conjectures in string theory, in the context of alternative theories of gravity with nonminimal coupling between matter and curvature. Our findings suggest that the slow-roll conditions are not compatible with the swampland conjectures for a vast range of inflationary solutions in these alternative theories of gravity.
Article
Physics, Fluids & Plasmas
A. E. Bernardini, O. Bertolami
Summary: The study investigates the Lotka-Volterra dynamics within the framework of Weyl-Wigner quantum mechanics. The research finds that the variables in LV dynamics can be interpreted as canonical variables in quantum mechanics, allowing for the understanding of the changes in the number of individuals in a prey-predator system. The results provide insights into how classical and quantum evolution coexist and offer a quantification of quantum analog effects.
Article
Optics
A. E. Bernardini, O. Bertolami
Summary: Phase-space features of one-dimensional systems with a constrained Hamiltonian are obtained analytically using Wigner functions and currents. Profiles for thermodynamic and Gaussian ensembles are identified, and the results are specialized to the Harper Hamiltonian system. This generalized Wigner approach serves as a probe for quantumness and classicality of Harper-like systems, and it can be extended to any quantum system described by specific Hamiltonians.
Article
Astronomy & Astrophysics
Riccardo March, Orfeu Bertolami, Marco Muccino, Claudio Gomes, Simone Dell'Agnello
Summary: We investigate a nonminimally coupled curvature-matter gravity theory that involves a Yukawa-type fifth force and a non-Newtonian extra force arising from the nonminimal coupling in the solar interior and atmosphere. The extra force depends on the spatial gradient of space-time curvature R. We examine the conditions under which these forces can be screened by the chameleon mechanism and be consistent with the Cassini measurement of the parametrized post-Newtonian parameter gamma. Constraints from spectroscopic observations of the solar atmosphere are also considered.
