arXiv subjects

Anton Yu. Alekseev

Publications and source records attributed to Anton Yu. Alekseev.

10 recordsLinked to original sources

arXiv2002

Non-commutative gauge theory of twisted D-branes

In this work we propose new non-commutative gauge theories that describe the dynamics of branes localized along twisted conjugacy classes on group manifolds. Our proposal is based on a careful analysis of the exact microscopic solution and it generalizes the matrix models (`fuzzy gauge theories') that are used to study e.g. the bound state formation of point-like branes in a curved background. We also construct a large number of classical solutions and interpret them in terms of condensation processes on branes localized along twisted conjugacy classes.

hep-th↗

arXiv2001

Open Strings and Non-commutative Geometry of Branes on Group Manifolds

In this contribution we review some recent work on the non-commutative geometry of branes on group manifolds. In particular, we show how fuzzy spaces arise in this context from an exact world-sheet description and we sketch the construction of a low-energy effective action for massless open string modes. The latter is given by a combination of a Yang-Mills and a Chern-Simons like functional on the fuzzy world-volume. It can be used to study condensation on various brane configurations in curved backgrounds.

hep-th↗

arXiv1998

Universality of transport properties in equilibrium, Goldstone theorem and chiral anomaly

We study transport in a class of physical systems possessing two conserved chiral charges. We describe a relation between universality of transport properties of such systems and the chiral anomaly. We show that the non-vanishing of a current expectation value implies the presence of gapless modes, in analogy to the Goldstone theorem. Our main tool is a new formula expressing currents in terms of anomalous commutators. Universality of conductance arises as a natural consequence of the nonrenormalization of anomalies. To illustrate our formalism we examine transport properties of a quantum wire in (1+1) dimensions and of massless QED in background magnetic field in (3+1) dimensions.

cond-mat.mes-hall↗

arXiv1998

On nonuniversal conductance quantization in high-quality quantum wires

We present a theoretical analysis of recent experimental results of Yacoby et al. on transport properties of high quality quantum wires. We suggest an explanation of observed deviations of the conductance from the universal value $2e^2/h$ per channel in the wire. We argue that at low temperatures and biases the deviation can be a consequence of anomalously enhanced backscattering of electrons entering the 2DEG from the wire and is not connected to intrinsic properties of 1DEG.

cond-mat.mes-hall↗

arXiv1997

Universality of equilibrium one-dimensional transport from gauge invariance

In this letter we address the question how interactions affect the DC conductance of a one-dimensional electron system not necessarily adequately described by the Luttinger model. Using a Laughlin type argument, we show that gauge invariance protects the universal value of the conductance of $e^2/h$ per channel per spin orientation if the system possesses two conserved charges conjugate to the chemical potentials of the external reservoirs.

cond-mat.mes-hall↗

arXiv1996

Quantum Moduli Spaces of Flat Connections

Using the formalism of discrete quantum group gauge theory, one can construct the quantum algebras of observables for the Hamiltonian Chern-Simons model. The resulting moduli algebras provide quantizations of the algebra of functions on the moduli spaces of flat connections on a punctured 2-dimensional surface. In this note we describe some features of these moduli algebras with special emphasis on the natural action of mapping class groups. This leads, in particular, to a closed formula for representations of the mapping class groups on conformal blocks.

q-alg↗

arXiv1996

Generalization of the Knizhnik-Zamolodchikov-Equations

In this letter we introduce a generalization of the Knizhnik- Zamolodchikov equations from affine Lie algebras to a wide class of conformal field theories (not necessarily rational). The new equations describe correlations functions of primary fields and of a finite number of their descendents. Our proposal is based on Nahm's concept of small spaces which provide adequate substitutes for the lowest energy subspaces in modules of affine Lie algebras. We explain how to construct the first order differential equations and investigate properties of the associated connections, thereby preparing the grounds for an analysis of quantum symmetries. The general considerations are illustrated in examples of Virasoro minimal models.

hep-th↗

arXiv1996

Comparing conductance quantization in quantum wires and Quantum Hall systems

We propose a new calculation of the DC conductance of a 1-dimensional electron system described by the Luttinger model. Our approach is based on the ideas of Landauer and Büttiker and on the methods of current algebra. We analyse in detail the way in which the system can be coupled to external reservoirs. This determines whether the conductance is renormalized or not. We show that although a quantum wire and a Fractional Quantum Hall system are described by the same effective theory, their coupling to external reservoirs is different. As a consequence, the conductance in the wire is quantized in integer units of $e^2/h$ per spin orientation whereas the Hall conductance allows for fractional quantization.

cond-mat↗

arXiv1996

The hyperbolic moduli space of flat connections and the isomorphism of symplectic multiplicity spaces

Let $G$ be a simple complex Lie group, $\alg{g}$ be its Lie algebra, $K$ be a maximal compact form of $G$ and $\alg{k}$ be a Lie algebra of $K$. We denote by $X\rightarrow \overline{X}$ the anti-involution of $\alg{g}$ which singles out the compact form $\alg{k}$. Consider the space of flat $\alg{g}$-valued connections on a Riemann sphere with three holes which satisfy the additional condition $\overline{A(z)}=-A(\overline{z})$. We call the quotient of this space over the action of the gauge group $\overline{g(z)}=g^{-1}(\overline{z})$ a \emph{hyperbolic} moduli space of flat connections. We prove that the following three symplectic spaces are isomorphic: 1. The hyperbolic moduli space of flat connections. 2. The symplectic multiplicity space obtained as symplectic quotient of the triple product of co-adjoint orbits of $K$. 3. The Poisson-Lie multiplicity space equal to the Poisson quotient of the triple product of dressing orbits of $K$.

dg-ga↗

arXiv1996

On Poisson actions of compact Lie groups on symplectic manifolds

Let $G_¶$ be a compact simple Poisson-Lie group equipped with a Poisson structure $¶$ and $(M, ø)$ be a symplectic manifold. Assume that $M$ carries a Poisson action of $G_¶$ and there is an equivariant moment map in the sense of Lu and Weinstein which acts to the dual Poisson-Lie group $G^*_¶$, $\m: M\rightarrow G^*_¶$. We prove that $M$ always possesses another symplectic form $\to$ so that the $G$-action preserves $\tildeø$ and there is a new moment map $μ= e^{-1} \circ \m: M\rightarrow \g^*$. Here $e$ is a universal (independent of $M$) invertible equivariant map $e: \g^*\rightarrow G^*_¶$. We suggest new short proves of the convexity theorem for the Poisson-Lie moment map, Poisson reduction theorem and the Ginzburg-Weinstein theorem on the isomorphism of $\g^*$ and $G^*_¶$ as Poisson spaces.

dg-ga↗