arXiv subjects

Haji Ahmedov

Publications and source records attributed to Haji Ahmedov.

12 recordsLinked to original sources

arXiv2025

Glow discharge induced reactions in mixtures of ozone and chlorodifluoromethane with atmospheric gases

The influence of extraterrestrial particles like cosmic radiation (CR) on the chemistry and ozone density in the Earth stratosphere is not well investigated and normally neglected in stratospheric chemistry models. Here we present the commissioning of a lab-based apparatus which aims at simulating conditions in the stratosphere in order to get better insight into the reactions induced by the secondary-particle showers from high-energetic CR which can reach low altitudes. Admixtures of ozone and the halocarbon CHClF2 (R22, chlorodifluoromethane) to atmospheric gases (N2, O2, Ar) were exposed to a glow discharge in the total pressure regime of a few hPa. According to the mass spectrometric analysis of the gas composition the discharge initiates significant ozone depletion by a factor four in the absence of R22. This depletion is strongly enhanced to two orders of magnitude in the presence of R22. The possible underlying reactions are discussed.

physics.plasm-ph↗

arXiv2013

Raman and non Raman EIT resonances in a degenerate four level system

We study coherence effects in an atom having three metastable levels and single life-time broadened upper state. Two laser fields couple ground states to an excited one and an radio-frequency (rf) field operates between ground state levels. We consider the case when the common level for the rf-field and one of the laser field (to which we refer as the probing field) transitions is twice degenerate. We predict a novel type of dark states (we call them non Raman dark states), which in contrary to Raman resonances, do not require the fulfillment of the two-photon resonance condition. We realize the configuration in the atomic hydrogen and show that non Raman resonances are determined by the geometry of the rf and probing field's polarizations. For ultra-cold atoms non Raman resonances arise when the polarization vectors of the fields are parallel or perpendicular to each other. For an atomic gas at room temperatures electromagnetically induced transparency (EIT) resonances associated with Raman and non Raman dark states are studied by taking into account spin-exchange relaxation in the ground state of the hydrogen atom. We establish properties of non Raman dark states by investigating the relation of EIT resonances to the polarization geometry.

quant-ph↗

arXiv2012

Type N Spacetimes as Solutions of Extended New Massive Gravity

We study algebraic type N spacetimes in the extended new massive gravity (NMG), considering both the Born-Infeld model (BI-NMG) and the model of NMG with any finite order curvature corrections. We show that for these spacetimes, the field equations of BI-NMG take the form of the massive (tensorial) Klein-Gordon type equation, just as it happens for ordinary NMG. This fact enables us to obtain the type N solution to BI-NMG, utilizing the general type N solution of NMG, earlier found in our work. We also obtain type N solutions to NMG with all finite order curvature corrections and show that, in contrast to BI-NMG, this model admits the critical point solutions, which are counterparts of "logarithmic" AdS pp-waves solutions of NMG.

hep-th↗

arXiv2011

Type D Solutions of 3D New Massive Gravity

In a recent reformulation of three-dimensional new massive gravity (NMG), the field equations of the theory consist of a massive (tensorial) Klein-Gordon type equation with a curvature-squared source term and a constraint equation. Using this framework, we present all algebraic type D solutions of NMG with constant and nonconstant scalar curvatures. For constant scalar curvature, they include homogeneous anisotropic solutions which encompass both solutions originating from topologically massive gravity (TMG), Bianchi types II, VIII, IX, and those of non-TMG origin, Bianchi types VI_{0} and VII_{0} . For a special relation between the cosmological and mass parameters, λ=m^2, they also include conformally flat solutions, and in particular those being locally isometric to the previously-known Kaluza-Klein type AdS_2xS^1 or dS_2x S^1 solutions. For nonconstant scalar curvature, all the solutions are conformally flat and exist only for λ=m^2 . We find two general metrics which possess at least one Killing vector and comprise all such solutions. We also discuss some properties of these solutions, delineating among them black hole type solutions.

hep-th↗

arXiv2010

The General Type N Solution of New Massive Gravity

We find the most general algebraic type N solution with non-vanishing scalar curvature, which comprises all type N solutions of new massive gravity in three dimensions. We also give the special forms of this solution, which correspond to certain critical values of the topological mass. Finally, we show that at the special limit, the null Killing isometry of the spacetime is restored and the solution describes AdS pp-waves.

hep-th↗

arXiv2010

Black String and Gödel type Solutions of Chern-Simons Modified Gravity

Chern-Simons (CS) modified gravity with a prescribed CS scalar field does not admit rotating black hole solutions with spherical topology of the horizon. In this paper, we show that it does admit rotating {\it black hole/string} solutions with cylindrical topology of the horizon and present two intriguing physical examples of such configurations. First, we show that the Banados-Teitelboim-Zanelli (BTZ) stationary black string, that is obtained by adding on a spacelike flat dimension to the BTZ black hole metric of three-dimensional gravity, solves the field equations of CS modified gravity with a specific source term and {\it irrespective of the choice of CS scalar field}. Next, we consider the Lemos solution for a rotating straight black string in general relativity and show that for the CS scalar field being a function of the radial coordinate alone, this solution persists in CS modified gravity. We also discuss two examples of Gödel type metrics in CS modified gravity by uplifting to four dimensions a general one-parameter family of Gödel type solutions of three-dimensional gravity. The first example is the usual Gödel solution of general relativity which also survives in CS modified gravity with the CS scalar field depending on two variables, the radial and the azimuthal coordinates. The second example represents a new nontrivial (non general relativity) Gödel type solution to the vacuum field equations of CS modified gravity. This solution originates from the respective vacuum solution of topologically massive gravity when extending it to four dimensions by adding on an extra spatial coordinate and choosing the CS scalar field as a linear function of this coordinate.

hep-th↗

arXiv2010

More on New Massive Gravity: Exact Solutions

We give a novel description of the recently proposed theory of new massive gravity (NMG) in three dimensions. We show that in terms of a Dirac type differential operator acting on the traceless Ricci tensor, the field equations of the theory reduce to the massive Klein-Gordon type equation with a curvature-squared source term and to a constraint equation. Under a certain relation between the source tensor and the traceless Ricci tensor, fulfilled for constant scalar curvature, the field equations of topologically massive gravity (TMG) can be thought of as the "square-root" of the massive Klein-Gordon type equation. Using this fact, we establish a simple framework for mapping all known algebraic types D and N solutions of TMG into NMG. We also present new exact solutions of algebraic types D and N which are only inherent in NMG.

hep-th↗

arXiv2010

Decoupling and Reduction in Chern-Simons Modified Gravity

We show that for four-dimensional spacetimes with a non-null hypersurface orthogonal Killing vector and for a Chern-Simons (CS) background (non-dynamical) scalar field, which is constant along the Killing vector, the source-free equations of CS modified gravity decouple into their Einstein and Cotton constituents. Thus, the model supports only general relativity solutions. We also show that, when the cosmological constant vanishes and the gradient of the CS scalar field is parallel to the non-null hypersurface orthogonal Killing vector of constant length, CS modified gravity reduces to topologically massive gravity in three dimensions. Meanwhile, with the cosmological constant such a reduction requires an appropriate source term for CS modified gravity.

hep-th↗

arXiv2009

Uniqueness of Rotating Charged Black Holes in Five-Dimensional Minimal Gauged Supergravity

We study a five-dimensional spacetime admitting, in the presence of torsion, a non-degenerate conformal Killing-Yano 2-form which is closed with respect to both the usual exterior differentiation and the exterior differentiation with torsion. Furthermore, assuming that the torsion is closed and co-closed with respect to the exterior differentiation with torsion, we prove that such a spacetime is the only spacetime given by the Chong-Cvetic-Lu-Pope solution for stationary, rotating charged black holes with two independent angular momenta in five-dimensional minimal gauged supergravity.

hep-th↗

arXiv2009

SUSY in the Spacetime of Higher-Dimensional Rotating Black Holes

General higher-dimensional rotating black hole spacetimes of any dimensions admit the Killing and Killing-Yano tensors, which generate the hidden symmetries just as in four-dimensional Kerr spacetime. We study these properties of the black holes using the formalism of supersymmetric mechanics of pseudo-classical spinning point particles. We present two nontrivial supercharges, corresponding to the Killing-Yano and conformal Killing-Yano tensors of the second rank. We demonstrate that an unusual extended Poisson-Dirac algebra of these supercharges results in two independent Killing tensors in spacetime dimensions $ D\geq 6 $, giving explicit examples for the Myers-Perry black holes in $ D = 6 $ dimensions.

hep-th↗

arXiv2009

Stationary Strings in the Spacetime of Rotating Black Holes in Five-Dimensional Minimal Gauged Supergravity

We examine the separability properties of the equation of motion for a stationary string near a rotating charged black hole with two independent angular momenta in five-dimensional minimal gauged supergravity. It is known that the separability problem for the stationary string in a general stationary spacetime is reduced to that for the usual Hamilton-Jacobi equation for geodesics of its quotient space with one dimension fewer. Using this fact, we show that the "effective metric" of the quotient space does not allow the complete separability for the Hamilton-Jacobi equation, albeit such a separability occurs in the original spacetime of the black hole. We also show that only for two special cases of interest the Hamilton-Jacobi equation admits the complete separation of variables and therefore the integrability for the stationary string motion in the original background: namely, when the black hole has zero electric charge or it has an arbitrary electric charge, but two equal angular momenta. We give the explicit expressions for the Killing tensors corresponding to these cases. However, for the general black hole spacetime the effective metric of the quotient space admits a conformal Killing tensor. We construct the explicit expression for this tensor.

hep-th↗

arXiv2009

Stationary Spinning Strings and Symmetries of Classical Spacetimes

We explore the symmetries of classical stationary spacetimes in terms of the dynamics of a spinning string described by a worldsheet supersymmetric action. We show that for stationary configurations of the string, the action reduces to that for a pseudo-classical spinning point particle in an effective space, which is a conformally scaled quotient space of the original spacetime. As an example, we consider the stationary spinning string in the Kerr-Newman spacetime, whose motion is equivalent to that of the spinning point particle in the three-dimensional effective space. We present the Killing tensor as well as the spin-valued Killing vector of this space. However, the nongeneric supersymmetry corresponding to the Killing-Yano tensor of the Kerr-Newman spacetime is lost in the effective space.

hep-th↗