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On the Stability of Spherically Symmetric Space-Times in Scalar-Tensor Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 K. A. Bronnikov, S. V. Bolokhov, M. V. Skvortsova, K. Badalov, R. Ibadov
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Quantization of Measure in Gravitation Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 V. Dzhunushaliev, V. Folomeev
Abstract Using the Radon–Nikodym theorem concerning the relation between any two measures, as well as the methods employed in loop quantum gravity, it is shown that in gravitation one can quantize any measure which is not even associated with metric. We have considered the simplest case where the proportionality coefficient between two operators of measure (the Radon–Nikodym derivative) is some function
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“New Inflation” for a Bianchi Type IX Cosmological Model with Rotation and Dark Energy Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 V. F. Panov, O. V. Sandakova, E. V. Kuvshinova
Abstract The first inflationary stage of the Bianchi type IX metric is considered for the case of inflation near the maximum potential according to the old terminology, “new inflation.” The evolution of rotation is studied with dark energy modeled by an anisotropic fluid.
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Phantom Dark Energy Nature of String-Fluid Cosmological Models in $$\boldsymbol{f(Q)}$$ -Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Dinesh Chandra Maurya
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Formation of Supermassive Nuclei of Black Holes in the Early Universe by the Mechanism of Scalar-Gravitational Instability. I. Local Picture $${}^{1}$$ Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Yu. G. Ignat’ev
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Dynamical Analysis of a Charged Spherical Star in $$\boldsymbol{R-}\boldsymbol{\beta}\boldsymbol{R}_{\boldsymbol{c}}\mathbf{tanh}\boldsymbol{(R/R_{c})+}\boldsymbol{\xi}\boldsymbol{RT}$$ Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 M. Z. Bhatti, Z. Yousaf, M. Yousaf
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On Algebraic Dependence of Cosmological Parameters Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Žarko Mijajlović, Danijela Branković
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Models of Anisotropic Stars in Spherically Symmetric Space-Time Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Ankita Jangid, B. S. Ratanpal, K. K. Venkataratnam
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GZK Cutoff in Presence of a Specified Modified Dispersion Relation Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Arash Majidian, Mehdi Jafari Matehkolaeer
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Proof for the Weak and the Strong Energy Conditions Theorems in Einstein–Yang–Mills Theories Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Alcides Garat
Abstract We present the manifest proof of the validity of the local weak and strong energy conditions in all Einstein–Maxwell–Yang–Mills space-times where nonnull electromagnetic and Yang–Mills fields are present. To this end, we make use of the new tetrads introduced previously. These new tetrads have remarkable properties in curved four-dimensional Lorentzian space-times. For example, they diagonalize
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Cosmological Model with Cosmic Transit Behavior in Brans-Dicke Theory Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Sunil K. Tripathy, Alaka Priyadarsini Sendha, Sasmita Kumari Pradhan, Zashmir Naik, B. Mishra
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Thick Fluid Disks Around Binary Black Holes Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 S. V. Chernov
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Photon Spheres near Dilatonic Dyon-Like Black Holes in a Model with Two Abelian Gauge Fields and Two Scalar Fields Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 V. D. Ivashchuk, A. N. Malybayev, G. S. Nurbakova, G. Takey
Abstract Dilatonic dyon-like black hole solutions with two (color) charges \(Q_{1}\) and \(Q_{2}\) (electric and magnetic ones) are considered in a gravitational 4D model with two scalar fields and two 2-forms. Two-dimensional dilatonic coupling vectors \(\vec{\lambda}_{i}\), \(i=1,2\), determining the model, obey the relation \(\vec{\lambda}_{1}\vec{\lambda}_{2}=1/2\). Circular null geodesics in the
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Studies of Density Contrast of Cold Dark Matter in Cosmological Radiation and Dark Energy Background: A Symmetry-Based Approach Gravit. Cosmol. (IF 0.9) Pub Date : 2023-11-23 Aritra Ganguly, Amitava Choudhuri
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Cosmological Solutions and Qualitative Analysis in the Generalized Scalar-Tensor Theory of Gravity with the Higgs Potential Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 S. V. Chervon, V. M. Zhuravlev, K. A. Bolshakova
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Topological Effects with Inverse Quadratic Yukawa Plus Inverse Square Potential on Eigenvalue Solutions Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 Faizuddin Ahmed
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Equations for Fields with Additional Fundamental Physical Constants Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 V. V. Khruschov
Abstract The author investigates the general Lie algebra of operators of coordinates, momenta, and Lorentz group generators, which can be used in quantum gravity, theories with a generalized uncertainty principle, double and triple relativity and theories with noncommutative space-time and momentum spaces. The structure constants of this algebra depend on the constants \(c\) and \(h\) as well as additional
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Revisiting Effective Einstein Equations on a 3-Brane in the Presence of Torsion Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 S. Khakshournia, R. Mansouri
Abstract The effective Einstein equations on a 3-brane embedded in a 5-dimensional Riemann–Cartan bulk space-time are revisited. Addressing the shortcomings in the hitherto published junction conditions on the brane in the presence of torsion, we have elaborated on our general form of the junction conditions recently published. Applying our general junction conditions, we formulate the effective Einstein
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Scalarly Charged Particles and Particle Interaction with the Higgs Potential Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 Yu. G. Ignat’ev
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Squeezed Thermal State Representation of the Inflaton and Particle Production in Bianchi Type-I Universe Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 Karam Chand
Abstract We use a single-mode squeezed thermal vacuum state formalism and examine the nature of a massive homogeneous scalar field minimally coupled to gravity in the framework of semiclassical gravity in a Bianchi type-I universe. We have obtained an estimate leading solution to the semiclassical Einstein equation for the Bianchi type-I universe showing that each scale factor in its respective direction
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Axially Symmetric Rotating Black Holes, Boyer–Lindquist Coordinates, and Regularity Conditions on Horizons Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 H. V. Ovcharenko, O. B. Zaslavskii
Abstract We consider the metric of an axially symmetric rotating black hole. We do not specify the concrete form of a metric and rely on its behavior near the horizon only. Typically, it is characterized (in the coordinates that generalize the Boyer–Lindquist ones) by two integers \(p\) and \(q\) that enter asymptotic expansions of the time and radial metric coefficients in the main approximation.
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Stability Analysis of Compactification in 3rd Order Lovelock Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 D. Chirkov, A. Toporensky
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Exact Cosmological Models in Modified $$\boldsymbol{f(R,L_{m})}$$ Gravity with Observational Constraints Gravit. Cosmol. (IF 0.9) Pub Date : 2023-09-04 Dinesh Chandra Maurya
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An Almost FLRW Universe as an Averaged Geometry in Macroscopic Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 Anish Agashe, Mustapha Ishak
Abstract It is well known that space-time averaging is an operation that does not commute with building the Einstein tensor. In the framework of Macroscopic gravity (MG), a covariant averaging procedure, this noncommutativity gives averaged field equations with an additional correction term known as back-reaction. It is important to explore whether such a term, even if known to be small, may or may
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Axisymmetric Stationary Space-Times of Constant Scalar Curvature in Four Dimensions Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 Rosikhuna F. Assafari, Emir S. Fadhilla, Bobby E. Gunara, Hasanuddin, Abednego Wiliardy
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Photonic Mode in a Space-Time with a Causal Loop: Comparison of D-CTC and S-CTC Models Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 A. V. Shepelin, V. A. Tomilin, L. V. Il’ichov
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On Geometrization of Classical Fields (Model of Embedded Spaces) Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 V. I. Noskov
Abstract The possibility of geometrization of the gravitational and electromagnetic fields in 4D Finsler space (the Model of Embedded Spaces—MES) is investigated. The model postulates a proper metric set of an element of distributed matter and asserts that space-time is a mutual physical embedding of such sets. The simplest MES geometry is constructed (its relativistic Finsler version) with a connection
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Trautman Problem and its Solution for Plane Waves in Riemann and Riemann–Cartan Spaces Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 O. V. Babourova, B. N. Frolov, M. S. Khetczeva, D. V. Kushnir
Abstract The Trautman problem determines the conditions under which GWs transfer the information contained in them in an invariant manner. According to the analogy between plane gravitational and electromagnetic waves, the metric tensor of a plane gravitational wave is invariant under the five-dimensional group \(G_{5}\), which does not change the null hypersurface of the plane wave front. The theorems
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Two Slingshots May Detect Ultraweak Features in the Sun’s Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 A. P. Yefremov
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Constraining Deceleration, Jerk and Transition Redshift Using Cosmic Chronometers, Type Ia Supernovae and the ISW Effect Gravit. Cosmol. (IF 0.9) Pub Date : 2023-06-10 Syed Faisal ur Rahman
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Peculiarities of the Motion of Spinning Particles in a Stationary Rotating Cosmological Model Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 V. G. Krechet, V. B. Oshurko, A. E. Kisser
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$$\boldsymbol{f(R,}\boldsymbol{\Sigma,}\boldsymbol{T)}$$ Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 M. A. Bakry, Shymaa K. Ibraheem
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The Bañados–Silk–West Effect with Immovable Particles Near Static Black Holes and Its Rotational Counterpart Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 O. B. Zaslavskii
Abstract The BSW effect implies that the energy \(E_{\textrm{c.m.}}\) in the center of mass frame of two particles colliding near a black hole can become unbounded. Usually, it is assumed that the particles move along geodesics or electrogeodesics. Instead, we consider another version of this effect. One particle is situated at rest near a static, generally speaking, distorted black hole. If another
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Coordinate-Independent Definition of Relative Velocity in Pseudo-Riemannian Space-Time: Implications for Special Cases Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 G. Ter-Kazarian
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Magnetically Charged AdS Black Holes and Joule–Thomson Expansion Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 S. I. Kruglov
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Arbitrary Static, Spherically Symmetric Space-Times as Solutions of Scalar-Tensor Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 K. A. Bronnikov, Kodir Badalov, Rustam Ibadov
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Static Weyssenhoff Fluid Sphere Models in Einstein–Cartan Theory of Gravitation Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 L. N. Katkar, D. R. Phadatare
Abstract Three physically reasonable static Weyssenhoff fluid sphere models have been obtained by solving the relevant field equations of the Einstein–Cartan theory of gravitation, when Weyssenhoff fluid is the source of spin and gravitation. The spin of the gravitating matter influences the fields of these fluid sphere models. The gravitational field of two of the models is proved to be of Petrov
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Hydrodynamic Consequences of Vlasov–Maxwell–Einstein Equations and Their Cosmological Applications Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 V. V. Vedenyapin, N. N. Fimin, V. M. Chechetkin
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Logamediate Inflation in DGP Cosmology Driven by a Non-Canonical Scalar Field Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 A. Ravanpak, G. F. Fadakar
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Algebrodynamics: Super-Conservative Collective Dynamics on a “Unique Worldline” and the Hubble Law Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 V. V. Kassandrov, Ildus Sh. Khasanov
Abstract We study the properties of roots of a polynomial system of equations which define a set of identical point particles located on a Unique Worldline (UW), in the spirit of the Wheeler–Feynman’s old conception. As a consequence of Vieta’s formulas, a great number of conservation laws are fulfilled for collective algebraic dynamics on the UW. These, besides the canonical ones, include the laws
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Coordinates in General Relativity: Orbit, Velocity, and Time form Perihelion to Aphelion Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 Wenbin Lin, Jie Li, Bo Yang
Abstract In general relativity, coordinate transformations are often made to simplify calculations, and theoretical predictions are calculated in some specific coordinates. We take the test particle’s motion in Schwarzschild space-time as an example, to illustrate that the solutions for orbit and velocity as well as the time from perihelion to aphelion depend on the coordinates employed for the calculations
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Lower-Dimensional Regge-Teitelboim Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 Anton Sheykin, Agata Grechko
Abstract We study modified gravity theory known as the Regge-Teitelboim approach, in which gravity is represented by the dynamics of a surface isometrically embedded in a flat bulk. We obtain some particular solutions of Regge-Teitelboim equations corresponding to a circularly symmetric vacuum 2+1-dimensional space-time. In contrast to GR, this vacuum space-time is not flat, so it is possible for the
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The Black Hole Event Horizon as a Limited Two-Way Membrane Gravit. Cosmol. (IF 0.9) Pub Date : 2023-04-04 Brian Jonathan Wolk
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Circular Time Delay around a Rotating and Nonrotating Mass Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 Elmo Benedetto, Gerardo Iovane
Abstract We make some considerations regarding the time delay of two light signals around a closed line, the well-known Sagnac effect. In our opinion, this experiment in flat space-time is simply a further test of Einstein’s equivalence principle. The revolving observer is physically equivalent to an observer at rest in a Lense-Thirring-like geometry.
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Ruling Out Inflation Driven by a Power Law Potential: Kinetic Coupling Does Not Help Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 N. A. Avdeev, A. V. Toporensky
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A Temporal Splitting Theorem for Chronological Spaces Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 Ali Bleybel
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Matter and Space. New Theory of Fields and Particles Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 V. M. Zhuravlev
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Gravity Assist as a Test of Relativistic Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 S. V. Bolokhov, K. A. Bronnikov, M. V. Skvortsova
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Appell’s Correspondence Unifies Gravity with Quantum Theory Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 Alexander Burinskii
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Single-Field Model of Gravitational-Scalar Instability. II. Black Hole Formation Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 Yu. G. Ignat’ev
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On the Black Hole Acceleration in the C-Metric Space-Time Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 F. L. Carneiro, S. C. Ulhoa, J. W. Maluf
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Relational Analysis of Dirac Equation in Momentum Representation Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 Anton V. Solov’yov
Abstract In terms of the relational approach to space-time geometry and physical interactions, we show that the Dirac equation for a free fermion in the momentum representation can be obtained starting from a binary system of complex relations (BSCR) between elements of two abstract sets. With the derivation performed, we show that the 4-dimensional pseudo-Euclidean momentum space is not needed a priori
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Squeezed Number State Representation of the Inflaton and Particle Production in the FRW Universe Gravit. Cosmol. (IF 0.9) Pub Date : 2022-11-25 Karam Chand
Abstract We use the single-mode coherent and squeezed number state formalism and analyze the nature of a massive homogeneous scalar field minimally coupled to gravity in the framework of semiclassical gravity in the Friedmann-Robertson-Walker (FRW) universe. We have obtained an estimate leading solution to the semiclassical Einstein equation for the FRW universe which shows the scale factor \(t^{2/3}\)
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From Maximum Force Via the Hoop Conjecture to Inverse Square Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 Christoph Schiller
Abstract The equivalence of maximum force \(c^{4}/4G\) and the field equations of general relativity provides a simple derivation of inverse square gravity. The derivation confirms the hoop conjecture and suggests a lack of gravitational physics beyond general relativity. Possible loopholes are pointed out.
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Mass Generation and Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 Mario Novello, Vicente Antunes
Abstract Despite the success of the Higgs mechanism to account for the generation of masses of the Standard Model (SM) elementary particles, the ultimate nature and origin of “mass” remain open questions in contemporary physics. From a foundational perspective, mass should be fundamentally related to the gravitational interaction and, according to Mach, with the structure of the Universe. In the present
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Single-Field Model of Gravitational-Scalar Instability. I. Evolution of Perturbations Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 Yu. G. Ignat’ev
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Loop Quantum Gravity: A Demystified View Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 Rakshit P. Vyas, Mihir J. Joshi
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Quintessence Behavior of New Tsallis Holographic Dark Energy in FRW Universe Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 Nisha Muttathazhathu Ali, Pankaj, Umesh Kumar Sharma
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Spherically Symmetric Solutions of a Chiral Self-Gravitating Model in $$\boldsymbol{f(R,\square R)}$$ Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 S. V. Chervon, I. V. Fomin, A. A. Chaadaev
Abstract We construct a chiral self-gravitating model corresponding to modified \(f(R,\square R)\) gravity following by application of the Lagrange multipliers method and a conformal transformation to obtain the model in the Einstein frame. Killing symmetries of the target space are found. Using a special case of a scaling transformation, we find examples of exact solutions with zero and constant potentials
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Inflation with Sterile Scalar Coupled to Massive Fermions and to Gravity Gravit. Cosmol. (IF 0.9) Pub Date : 2022-09-06 Jéssica S. Martins, Oliver F. Piattella, Ilya L. Shapiro, Alexei A. Starobinsky