arXiv subjects

G. Nugmanova

Publications and source records attributed to G. Nugmanova.

12 recordsLinked to original sources

arXiv2026

Integrable Zhaidary equations: reductions and gauge equivalence

The present work addresses the study and characterization of the integrability of some generalized spin systems (ISS) in 1+1 dimensions. Lax representations for these ISS are successfully obtained. The gauge equivalent counterparts of these integrable ISS are presented. Finally, we consider Zhanbota transcendents and some integrable Zhanbota equations. In particular, the gauge equivalence between some Zhanbota equations and the six Painleve equations is established.

nlin.SI↗

arXiv2025

Integrability, geometry and wave solutions of some Kairat equations

In this paper, we study some Kairat equations. The relation between the motion of curves and Kairat equations is established. The geometrical equivalence between the Kairat-I equation and the Kairat-II equation is proved. We also proves that these equations is gauge equivalent to each other. Three types traveling wave solutions of the Kairat-II equation as well as its some integrals of motion are found. The techniques used in this paper can be adopted to study other integrable spin systems and nonlinear models. In particular, using these methods we study some Zhanbota equations.

nlin.SI↗

arXiv2025

Integrable Kuralay equations: geometry, solutions and generalizations

In this paper, we study the Kuralay equations, namely, the Kuralay-I equation (K-IE) and the Kuralay-II equation (K-IIE). The integrable motion of space curves induced by these equations is investigated. The gauge equivalence between these two equations is established. With the help of the Hirota bilinear method, the simplest soliton solutions are also presented. The nonlocal and dispersionless versions of the K-IE and K-IIE are considered.

nlin.SI↗

arXiv2024

FLRW Cosmology in Metric-Affine $F(R,Q)$ Gravity

We investigate some FLRW cosmological models in the context of Metric-Affine $F(R,Q)$ gravity, as proposed in [arXiv:1205.52666]. Here, $R$ and $Q$ are the curvature and nonmetricity scalars using non-special connections, respectively. We get the modified field equations using a flat Friedmann-Lemaître-Robertson-Walker (FLRW) metric. We then find a connection between the Hubble constant $H_{0}$, the density parameter $Ω_{m0}$, and the other model parameters in two different situations involving scalars $u$ and $w$. Next, we used new observational datasets, such as the cosmic chronometer (CC) Hubble datasets and the Pantheon SNe Ia datasets, to determine the optimal model parameter values through MCMC analysis. Using these best-fit values of model parameters, we have discussed the results and behavior of the derived models. We have also discussed the AIC and BIC criteria for the derived models in the context of $Λ$CDM. We have found that the geometrical sector dark equation of state parameter $ω_{de}$ behaves just like a dark energy candidate. We have found that both models are transit phase models and Model-I approaches to the Lambda CDM model in the late-time universe and Model-II approaches to quintessence scenarios.

gr-qc↗

arXiv2024

Metric-affine Myrzakulov gravity theories with Gauss-Bonnet and boundary term scalars

In this paper, we consider some metric-affine Myrzakulov gravity (MG) theories with Gauss-Bonnet scalars. Also we consider the MG theories with the boundary term scalars. Note that these MG theories with the Gauss-Bonnet and boundary term scalars were proposed in [arXiv:1205.5266]. Some examples of Metric-Affine Gravity (MAG) theories are reviewed in the context of the $F(R,T,Q,{\cal T}, {\cal D})$ type models. Then the generalized MAG theory with the curvature, torsion and nonmetricity (the so-called MG-VIII) was studied. For the FRW spacetime case, in particular, the Lagrangian, Hamilatonian and gravitational equations are obtained. The particular case $F(R,T)=αR+βT+μQ+ν{\cal T}$ is investigated in detail. In quantum case, the corresponding Wheeler-DeWitt equation is obtained. Finally, some gravity theories with the curvature, torsion and nonmetricity are presented.

gr-qc↗

arXiv2024

Myrzakulov $F(T,Q)$ gravity: cosmological implications and constraints

In this paper, we investigate some exact cosmological models in Myrzakulov $F(T,Q)$ gravity or the Myrzakulov gravity-III (MG-III) proposed in [arXiv:1205.5266], with observational constraints. The MG-III gravity is some kind of unification of two known gravity theories, namely, the $F(T)$ gravity and the $F(Q)$ gravity. The field equations of the MG-III theory are obtained by regarding the metric tensor and the general affine connection as independent variables. We then focus on the particular case in which the $F(T,Q)$ function characterizing the aforementioned metric-affine models is linear that is $F(T,Q)=λT+μQ$. We investigate this linear case and consider a Friedmann-Lemaître-Robertson-Walker background to study cosmological aspects and applications. We have obtained three exact solutions of the modified field equations in different cases $T$ and $Q$, in the form of Hubble function $H(t)$ and scale factor $a(t)$ and placed observational constraints on it through the Hubble $H(z)$ datasets on it using the MCMC analysis. We have investigated the deceleration parameter $q(z)$, effective EoS parameters and a comparative study of all three models with $Λ$CDM model has been carried out.

gr-qc↗

arXiv2023

Nonlocal Reductions of a Generalized Heisenberg Ferromagnet Equation

We study nonlocal reductions of coupled equations in $1+1$ dimensions of the Heisenberg ferromagnet type. The equations under consideration are completely integrable and have a Lax pair related to a linear bundle in pole gauge. We describe the integrable hierarchy of nonlinear equations related to our system in terms of generating operators. We present some special solutions associated with four distinct discrete eigenvalues of the scattering operator. Using Lax pair diagonalization method, we derive recurrence formulas for the conserved densities and find the first two simplest conserved densities.

nlin.SI↗

arXiv2022

Integrable motion of anisotropic space curves and surfaces induced by the Landau-Lifshitz equation

In this paper, we have studied the geometrical formulation of the Landau-Lifshitz equation (LLE) and established its geometrical equivalent counterpart as some generalized nonlinear Schrödinger equation. When the anisotropy vanishes, from this result follows the well-known results corresponding for the isotropic case, i.e. to the Heisenberg ferromagnet equation and the focusing nonlinear Schrödinger equation. The relations between the LLE and the differential geometry of space curves in the local and nonlocal cases are studied. Using the well-known Sym-Tafel formula, the soliton surfaces induced by the LLE are briefly considered.

nlin.SI↗

arXiv2015

Darboux Transformation and Exact Solutions of the integrable Heisenberg ferromagnetic equation with self-consistent potentials

Integrable Heisenberg ferromagnetic equations are an important subclass of integrable systems. The M-XCIX equation is one of a generalizations of the Heisenberg ferromagnetic equation and are integrable. In this paper, the Darboux transformation of the M-XCIX equation is constructed. Using the DT, a 1-soliton solution of the M-XCIX equation is presented.

nlin.SI↗

arXiv2015

Integrable (2+1)-Dimensional Spin Models with Self-Consistent Potentials

Integrable spin systems possess interesting geometrical and gauge invariance properties and have important applications in applied magnetism and nanophysics. They are also intimately connected to the nonlinear Schrödinger family of equations. In this paper, we identify three different integrable spin systems in (2 + 1) dimensions by introducing the interaction of the spin field with more than one scalar potential, or vector potential, or both. We also obtain the associated Lax pairs. We discuss various interesting reductions in (2 + 1) and (1 + 1) dimensions. We also deduce the equivalent nonlinear Schrödinger family of equations, including the (2 + 1)-dimensional version of nonlinear Schrödinger--Hirota--Maxwell--Bloch equations, along with their Lax pairs.

nlin.SI↗

arXiv2014

Darboux Transformation and Exact Solutions of the Myrzakulov-Lakshmanan-II Equation

The Myrzakulov-Lakshmanan-II (ML-II) equation is one of a (2+1)-dimensional generalizations of the Heisenberg ferromagnetic equation. It is integrable and has a non-isospectral Lax representation. In this paper, the Darboux transformation (DT) for the ML-II equation is constructed. Using the DT, the 1-soliton and 2-soliton solutions of the ML-II equation are presented.

nlin.SI↗

arXiv2011

Reconstruction of f-essence and fermionic Chaplygin gas models of dark energy

Recently, it was proposed a new fermionic model of dark energy, the so-called f-essence. In this work, we explicitly reconstruct the different f-essence models. In particular, these models include the fermionic Chaplygin gas and the fermionic generalized Chaplygin gas models of dark energy. We also derive the equation of state parameter of the selected f-essence models.

gr-qc↗