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S. Habib Mazharimousavi

Publications and source records attributed to S. Habib Mazharimousavi.

At least 127 records · Page 7Linked to original sources
arXiv2011

2+1 dimensional magnetically charged solutions in Einstein - Power - Maxwell theory

We obtain a class of magnetically charged solutions in 2+1 dimensional Einstein - Power - Maxwell theory. In the linear Maxwell limit, such horizonless solutions are known to exist. We show that in 3D geometry, black hole solutions with magnetic charge does not exist even if it is sourced by power-Maxwell field. Physical properties of the solution with particular power k of the Maxwell field is investigated. The true timelike naked curvature singularity develops when k>1 which constitutes one of the striking effects of the power Maxwell field. For specific power parameter k, the occurrence of timelike naked singularity is analysed in quantum mechanical point of view. Quantum test fields obeying the Klein - Gordon and the Dirac equations are used to probe the singularity. It is shown that the class of static pure magnetic spacetime in the power Maxwell theory is quantum mechanically singular when it is probed with fields obeying Klein-Gordon and Dirac equations in the generic case.

gr-qc↗
arXiv2011

Black hole solutions in f(R) gravity coupled with non-linear Yang-Mills field

It is shown that in the static, spherically symmetric spacetime the problem of metric f(R) gravity coupled with non-linear Yang-Mills (YM) field constructed from the Wu-Yang ansatz as source, can be solved in all dimensions. By non-linearity it is meant that the YM Lagrangian depends arbitrarily on its invariant. A particular form is considered to be in the power-law form with limit of the standard YM theory. The formalism admits black hole solutions with single or double horizons in which f(R) can be obtained, in general numerically. In 6-dimensional case we obtain an exact solution given by f(R)=\surdR gravity that couples with the YM field in a consistent manner.

gr-qc↗
arXiv2011

d-dimensional non-asymptotically flat thin-shell wormholes in Einstein-Yang-Mills-Dilaton gravity

Thin-shell wormholes in Einstein-Yang-Mills-dilaton (EYMD) gravity are considered. We show that a non-asymptotically flat (NAF) black hole solution of the d-dimensional EYMD theory provides stable thin-shell wormholes which are supported entirely by exotic matter. The presence of dilaton makes the spacetime naturally NAF, and with our conclusion it remains still open to construct wormholes supported by normal matter between two such spacetimes.

gr-qc↗
arXiv2011

Higher dimensional thin-shell wormholes in Einstein-Yang-Mills-Gauss-Bonnet gravity

We present thin-shell wormhole solutions in Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory in higher dimensions d\geq5. Exact black hole solutions are employed for this purpose where the radius of thin-shell lies outside the event horizon. For some reasons the cases d=5 and d>5 are treated separately. The surface energy-momentum of the thin-shell creates surface pressures to resist against collapse and rendering stable wormholes possible. We test the stability of the wormholes against spherical perturbations through a linear energy-pressure relation and plot stability regions. Apart from this restricted stability we investigate the possibility of normal (i.e. non-exotic) matter which satisfies the energy conditions. For negative values of the Gauss-Bonnet (GB) parameter we obtain such physical wormholes.

gr-qc↗
arXiv2010

Simple system to measure the Earth's magnetic field

Our aim in this proposal is by using the Faraday's law of induction as a simple lecture demonstration to measure the Earth's magnetic field (B). This will also enable the students to learn about how electric power is generated from the rotational motion. Obviously the idea is not original, yet it may be attractive in the sense that no sophisticated devices are used.

physics.pop-ph↗
arXiv2010

Solution for Static, Spherically Symmetric Lovelock Gravity Coupled with Yang-Mills Hierarchy

The hierarchies of both Lovelock gravity and power-Yang-Mills field are combined through gravity in a single theory. In static, spherically symmetric ansatz exact particular integrals are obtained in all higher dimensions. The advantage of such hierarchies is the possibility of choosing coefficients, which are arbitrary otherwise, to cast solutions into tractable forms. To our knowledge the solutions constitute the most general spherically symmetric metrics that incorporate complexities both of Lovelock and Yang-Mills hierarchies within the common context. A large portion of our general class of solutions concern and addresses to black holes for which specific examples are given. Thermodynamical behaviors of the system is briefly discussed in particular dimensions.

gr-qc↗
arXiv2010

Domain-Walls in Einstein-Gauss-Bonnet Bulk

We investigate the dynamics of a d-dimensional domain wall (DW) in a d+1-dimensional Einstein-Gauss-Bonnet (EGB) bulk. Exact effective potential induced by the Gauss-Bonnet (GB) term on the wall is derived. In the absence of the GB term we recover the familiar gravitational and anti-harmonic oscillator potentials. Inclusion of the GB correction gives rise to a minimum radius of bounce for the Friedmann-Robertson-Walker (FRW) universe expanding with a negative pressure on the DW.

gr-qc↗
arXiv2010

Theorem to generate Einstein-Non Linear Maxwell Fields

We present a theorem in d-dimensional static, spherically symmetric spacetime in generic Lovelock gravity coupled with a non-linear electrodynamic source to generate solutions. The theorem states that irrespective of the order of the Lovelock gravity and non-linear Maxwell (NLM) Lagrangian, for the pure electric field case the NLM equations are satisfied by virtue of the Einstein-Lovelock equations. Applications of the theorem, specifically to the study of black hole solutions in Chern-Simons (CS) theory is given. Radiating version of the theorem has been considered, which generalizes the Bonnor-Vaidya (BV) metric to the Lovelock gravity with a NLM field as a radiating source. We consider also the radiating power - Maxwell source (i.e. $\(F_{μν}F^{μν}\)^{q},$ $q=$ finely - tuned constant) within the context of Lovelock gravity.

gr-qc↗
arXiv2010

Stability of thin-shell wormholes supported by ordinary matter in Einstein-Maxwell-Gauss-Bonnet gravity

Recently in (Phys. Rev. D 76, 087502 (2007) and Phys. Rev. D 77, 089903(E) (2008)) a thin-shell wormhole has been introduced in 5-dimensional Einstein-Maxwell-Gauss-Bonnet (EMGB) gravity which was supported by normal matter. We wish to consider this solution and investigate its stability. Our analysis shows that for the Gauss-Bonnet (GB) parameter $α<0,$ stability regions form for a narrow band of finely-tuned mass and charge. For the case $α>0$, we iterate once more that no stable, normal matter thin-shell wormhole exists.

gr-qc↗
arXiv2010

Revisiting the dyonic Majumdar-Papapetrou black holes

We extend the Majumdar-Papapetrou (MP) solution of the Einstein-Maxwell (EM) equations which is implied generally for static electric charge in non-rotating metrics to encompass equally well magnetic charges. In the absence of Higgs and non-Abelian gauge fields, 'dyonic' is to be understood in this simpler sense. Cosmologically this may have far-reaching consequences, to the extent that existence of multi-magnetic monopole black holes may become a reality in our universe. Infalling charged particle geodesics may reveal, through particular integrals, their inner secrets which are screened from our observation.

gr-qc↗
arXiv2010

Dilatonic interpolation between Reissner-Nordstrom and Bertotti-Robinson spacetimes with physical consequences

We give a general class of static, spherically symmetric, non-asymptotically flat and asymptotically non-(anti) de Sitter black hole solutions in Einstein-Maxwell-Dilaton (EMD) theory of gravity in 4-dimensions. In this general study we couple a magnetic Maxwell field with a general dilaton potential, while double Liouville-type potentials are coupled with the gravity. We show that the dilatonic parameters play the key role in switching between the Bertotti-Robinson and Reissner-Nordström spacetimes. We study the stability of such black holes under a linear radial perturbation, and in this sense we find exceptional cases that the EMD black holes are unstable. In continuation we give a detailed study of the spin-weighted harmonics in dilatonic Hawking radiation spectrum and compare our results with the previously known ones. Finally, we investigate the status of resulting naked singularities of our general solution when probed with quantum test particles.

gr-qc↗
arXiv2009

Generating Static Spherically Symmetric Black-holes in Lovelock Gravity

Generalization of a known theorem to generate static, spherically symmetric black-hole solutions in higher dimensional Lovelock gravity is presented. Particular limits, such as Gauss-Bonnet (GB) and/or Einstein-Hilbert (EH) in any dimension $N$ yield all the solutions known to date with an energy-momentum. In our generalization, with special emphasis on the third order Lovelock gravity, we have found two different class of solutions characterized by the matter field parameter. Several particular cases are studied and properties related to asymptotic behaviours are discussed. Our general solution which covers topological black holes as well, splits naturally into distinct classes such as Chern-Simon (CS) and Born-Infeld (BI) in higher dimensions. The occurence of naked singularities are studied and it is found that, the spacetime behaves nonsingular in quantum mechanical sense when it is probed with quantum test particles. The theorem is extended to cover Bertotti-Robinson (BR) type solutions in the presence of the GB parameter alone. Finally we prove also that extension of the theorem for a scalar-tensor source of higher dimensions $(N>4)$ fails to work.

gr-qc↗
arXiv2009

Lovelock black holes with a power-Yang-Mills source

We consider the standard Yang-Mills (YM) invariant raised to the power q, i.e., $(F_{μν}^{(a)}F^{(a) μν})^{q}$ as the source of our geometry and investigate the possible black hole solutions. How does this parameter q modify the black holes in Einstein-Yang-Mills (EYM) and its extensions such as Gauss-Bonnet (GB) and the third order Lovelock theories? The advantage of such a power q (or a set of superposed members of the YM hierarchies) if any, may be tested even in a free YM theory in flat spacetime. Our choice of the YM field is purely magnetic in any higher dimensions so that duality makes no sense. In analogy with the Einstein-power-Maxwell theory, the conformal invariance provides further reduction, albeit in a spacetime for dimensions of multiples of 4.

gr-qc↗
arXiv2009

Black holes and the classical model of a particle in Einstein non-linear electrodynamics theory

Modified by a logarithmic term, the non-linear electrodynamics (NED) model of the Born-Infeld (BI) action is reconsidered. Unlike the standard BI action, this choice provides interesting integrals of the Einstein-NED equations. It is found that the spherical matching process for a regular black hole entails indispensable surface stresses that vanish only for a specific value of the BI parameter. This solution represents a classical model of an elementary particle whose radius coincides with the horizon. In flat space time, a charged particle becomes a conducting shell with a radius proportional to the BI parameter.

gr-qc↗
arXiv2009

A quasi-free position-dependent-mass jump and self-scattering correspondence

A quasi-free quantum particle endowed with Heaviside position dependent mass jump is observed to experience scattering effects manifested by its by-product introduction of the derivative of the Dirac's-delta point dipole interaction. Using proper parametric mappings, the reflection and transmission coefficients are obtained. A new ordering ambiguity parameters set, as the only feasibly admissible within the current methodical proposal, is suggested.

quant-ph↗
arXiv2009

N-Dimensional non-abelian dilatonic, stable black holes and their Born-Infeld extension

We find large classes of non-asymptotically flat Einstein-Yang-Mills-Dilaton (EYMD) and Einstein-Yang-Mills-Born-Infeld-Dilaton (EYMBID) black holes in N-dimensional spherically symmetric spacetime expressed in terms of the quasilocal mass. Extension of the dilatonic YM solution to N-dimensions has been possible by employing the generalized Wu-Yang ansatz. Another metric ansatz, which aided in finding exact solutions is the functional dependence of the radius function on the dilaton field. These classes of black holes are stable against linear radial perturbations. In the limit of vanishing dilaton we obtain Bertotti-Robinson (BR) type metrics with the topology of $AdS_{2}\times S^{N-2}.$ Since connection can be established between dilaton and a scalar field of Brans-Dicke (BD) type we obtain black hole solutions also in the Brans-Dicke-Yang-Mills (BDYM) theory as well.

gr-qc↗