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A. Sedrakyan

Publications and source records attributed to A. Sedrakyan.

At least 37 records · Page 2Linked to original sources
arXiv2004

Perturbative test of single parameter scaling for 1D random media

Products of random matrices associated to one-dimensional random media satisfy a central limit theorem assuring convergence to a gaussian centered at the Lyapunov exponent. The hypothesis of single parameter scaling states that its variance is equal to the Lyapunov exponent. We settle discussions about its validity for a wide class of models by proving that, away from anomalies, single parameter scaling holds to lowest order perturbation theory in the disorder strength. However, it is generically violated at higher order. This is explicitely exhibited for the Anderson model.

math-ph↗
arXiv2004

An Integrable Model with non-reducible three particle R-Matrix

We define an integrable lattice model which, in the notation of Yang, in addition to the conventional 2-particle $R$-matrices also contains non-reducible 3-particle $R$-matrices. The corresponding modified Yang-Baxter equations are solved and an expression for the transfer matrix is found as a normal ordered exponential of a (non-local) Hamiltonian.

cond-mat.stat-mech↗
arXiv2003

On the theory of plateau-plateau transitions in Quantum Hall Effect

The Lagrangian (action) formulation of the Chalker-Coddington network model for plateau-plateau transitions in quantum Hall effect is presented based on a model of fermions hopping on Manhattan Lattice ($ML$). The dimensionless Landauer resistance is considered and its average is calculated over the random U(1) phases with constant distribution on the circle. The Lagrangian of the resultant model on $ML$ is found and the corresponding $R$-matrix is written down. It appeared, that this model is integrable, rising hope to investigate physics of plateau- plateau transitions by the exact method of powerful Algebraic Bethe Ansatz $(ABA)$.

cond-mat.mes-hall↗
arXiv2002

Multi-leg integrable ladder models

We construct integrable spin chains with inhomogeneous periodic disposition of the anisotropy parameter. The periodicity holds for both auxiliary (space) and quantum (time) directions. The integrability of the model is based on a set of coupled Yang-Baxter equations. This construction yields P-leg integrable ladder Hamiltonians. We analyse the corresponding quantum group symmetry.

hep-th↗
arXiv2001

Integrable chain models with staggered R-matrices

The technique of construction on Manhattan lattice (ML) the fermionic action for Integrable models is presented. The Sign-Factor of 3D Ising model (SF of 3DIM) and Chalker-Coddington-s phenomenological model (CCM) for the edge excitations in Hall effect are formulated in this way. The second one demonstrates the necessity to consider the inhomogeneous models with staggered R-matrices. The disorder over the U(1) phases is taken into account and staggered Hubbard type of model is obtained. The technique is developed to construct the integrable models with staggered R-matrices. The disorder over the U(1) phases is taken into account and staggered Hubbard type of model is obtained. The technique is developed to construct the integrable models with staggered disposition of R-matrices.

cond-mat.mes-hall↗
arXiv2001

Integrable XYZ Model with Staggered Anisotropy Parameter

We apply to the XYZ model the technique of construction of integrable models with staggered parameters, presented recently for the XXZ case. The solution of modified Yang-Baxter equations is found and the corresponding integrable zig-zag ladder Hamiltonian is calculated. The result is coinciding with the XXZ case in the appropriate limit.

hep-th↗
arXiv2001

3D Ising Model on Dual BCC Lattice: the Sign-Factor

The 3d Ising model on a regular cubic lattice can be expressed in terms of an SU(2) 2d fermionic model with a $Z_2$-fluxes. We modify the model such that it is defined on the dual to a body centered cubic lattice. The advantage of this lattice is that 2d embedded surfaces have no selfintersections, thus partially avoiding the Sign-factor problem associated with the 2d fermionoc models related to the 3d Ising model. Rather than solving the full SU(2) fermionic theory on this lattice we study the simpler model of scalar fermions and find the spectrum of excitations. The model has no mass gap. We reformulate the model using the R-formalism and a new interesting structure appears due to the necessity of introducing a three-paticle matrix $R^{(3)}_{ijk}$. It encodes the essential character of the Sign-factor. We analyse the integrability properties of this class of models.

cond-mat↗
arXiv2001

Generalization of the U_q(gl(N)) algebra and staggered models

We develop a technique of construction of integrable models with a Z_2 grading of both the auxiliary (chain) and quantum (time) spaces. These models have a staggered disposition of the anisotropy parameter. The corresponding Yang-Baxter Equations are written down and their solution for the gl(N) case are found. We analyze in details the N=2 case and find the corresponding quantum group behind this solution. It can be regarded as quantum U_{q,B}(gl(2)) group with a matrix deformation parameter qB with (qB)^2=q^2. The symmetry behind these models can also be interpreted as the tensor product of the (-1)-Weyl algebra by an extension of U_q(gl(N)) with a Cartan generator related to deformation parameter -1.

hep-th↗
arXiv2000

Integrable Ladder t-J Model with Staggered Shift of the Spectral Parameter

The generalization of the Yang-Baxter equations (YBE) in the presence of Z_2 grading along both chain and time directions is presented and an integrable model of t-J type with staggered disposition along a chain of shifts of the spectral parameter is constructed. The Hamiltonian of the model is computed in fermionic formulation. It involves three neighbour site interactions and therefore can be considered as a zig-zag ladder model. The Algebraic Bethe Ansatz technique is applied and the eigenstates, along with eigenvalues of the transfer matrix of the model are found. In the thermodynamic limit, the lowest energy of the model is formed by the quarter filling of the states by fermions instead of usual half filling.

hep-th↗
arXiv2000

Integrable Chain Model with Additional Staggered Model Parameter

The generalization of the Yang-Baxter equations (YBE) in the presence of Z_2 grading along both chain and time directions is presented. The XXZ model with staggered disposition along a chain of both, the anisotropy \pmΔ, as well as shifts of the spectral parameters are considered and the corresponding integrable model is constructed. The Hamiltonian of the model is computed in fermionic and spin formulations. It involves three neighbour site interactions and therefore can be considered as a zig-zag ladder model. The Algebraic Bethe Ansatz technique is applied and the eigenstates, along with eigenvalues of the transfer matrix of the model are found. The model has a free fermionic limit at Δ=0 and the integrable boundary terms are found in this case. This construction is quite general and can be applied to other known integrable models.

hep-th↗
arXiv2000

Electron states in a one-dimensional random binary alloy

We present a model for alloys of compound semiconductors by introducing a one-dimensional binary random system where impurities are placed in one sublattice while host atoms lie on the other sublattice. The source of disorder is the stochastic fluctuation of the impurity energy from site to site. Although the system is one-dimensional and random, we demonstrate analytical and numerically the existence of extended states in the neighborhood of a given resonant energy, which match that of the host atoms.

cond-mat.dis-nn↗
arXiv1999

Delocalization of states in two component superlattices with correlated disorder

Electron and phonon states in two different models of intentionally disordered superlattices are studied analytically as well as numerically. The localization length is calculated exactly and we found that it diverges for particular energies or frequencies, suggesting the existence of delocalized states for both electrons and phonons. Numerical calculations for the transmission coefficient support the existence of these delocalized states.

cond-mat↗
arXiv1998

Edge Excitations of an Incompressible Fermionic Liquid in a Disorder Magnetic Field

The model of lattice fermions in 2+1 dimensional space is formulated, the critical states of which are lying in the basis of such physical problems, as 3D Ising Model(3DIM) and the edge excitations in the Hall effect. The action for this exitations coincides with the action of so called sign-factor model in 3DIM at one values of its parameters, and represent a model for the edge excitations, which are responsible for the plato transitions in the Hall effect, at other values. The model can be formulated also as a loop gas models in 2D, but unlikely the O(n) models, where the loop fugacity is real, here we have directed (clochwise and conterclochwise) loops and phase factors $e^{\pm 2π{p \over q} i}$ for them. The line of phase transitions in the parametric space will be found and corresponding continuum limits of this models will be constructed. It appears, that besides the ordinary critical line, which separates the dense and diluted phases of the models(like in ordinary O(n) models), there is a line, which corresponds to the full covering of the space by curves. The N=2 twisted superconformal models with SU(2)/U(1) coset model coupling constant $k={q \over p}-2$ describes this states.

cond-mat↗
arXiv1998

Bethe Ansatz and Thermodynamic Limit of Affine Quantum Group Invariant Extensions of the t-J Model

We have constructed a one dimensional exactly solvable model, which is based on the t-J model of strongly correlated electrons, but which has additional quantum group symmetry, ensuring the degeneration of states. We use Bethe Ansatz technique to investigate this model. The thermodynamic limit of the model is considered and equations for different density functions written down. These equations demonstrate that the additional colour degrees of freedom of the model behave as in a gauge theory, namely an arbitrary distribution of colour indices over particles leave invariant the energy of the ground state and the excitations. The $S$-matrix of the model is shown to be the product of the ordinary $t-J$ model $S$-matrix and the unity matrix in the colour space.

cond-mat.supr-con↗
arXiv1997

A New Family of Integrable Extended Multi-band Hubbard Hamiltonians

We consider exactly solvable 1d multi-band fermionic Hamiltonians, which have affine quantum group symmetry for all values of the deformation. The simplest Hamiltonian is a multi-band t-J model with vanishing spin-spin interaction, which is the affinization of an underlying XXZ model. We also find a multi-band generalization of standard t-J model Hamiltonian.

cond-mat↗
arXiv1997

Family of Affine Quantum Group Invariant Integrable Extensions of Hubbard Hamiltonian

We construct the family of spin chain Hamiltonians, which have affine quantum group symmetry. Their eigenvalues coincide with the eigenvalues of the usual spin chain Hamiltonians, but have the degeneracy of levels, corresponding to affine quantum group. The space of states of these spin chains is formed by the tensor product of fully reducible representations of quantum group. The fermionic representations of constructed spin chain Hamiltonians show that we have new extensions of Hubbard Hamiltonians. All of them are integrable and have affine quantum group symmetry. The exact ground state of a such type model is presented, exhibiting superconducting behavior via eta-pairing mechanism.

cond-mat↗
arXiv1996

The measure in three dimensional Nambu-Goto string theory

We show that the measure of the three dimensional Nambu-Goto string theory has a simple decomposition as a measure on two parameter group of induced area-preserving transformations of the immersed surface and a trivial measure for the area of the surface.

hep-th↗