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B. Sazdovic

Publications and source records attributed to B. Sazdovic.

16 recordsLinked to original sources
arXiv2012

Dirichlet boundary conditions in type IIB superstring theory and fermionic T-duality

In this article we investigate the relation between consequences of Dirichlet boundary conditions (momenta noncommutativity and parameters of the effective theory) and background fields of fermionic T-dual theory. We impose Dirichlet boundary conditions on the endpoints of the open string propagating in background of type IIB superstring theory with constant background fields. We showed that on the solution of the boundary conditions the momenta become noncommutative, while the coordinates commute. Fermionic T-duality is also introduced and its relation to noncommutativity is considered. We use compact notation so that type IIB superstring formally gets the form of the bosonic one with Grassman variables. Then momenta noncommutativity parameters are fermionic T-dual fields. The effective theory, the initial theory on the solution of boundary conditions, is bilinear in the effective coordinates, odd under world-sheet parity transformation. The effective metric is equal to the initial one and terms with the effective Kalb-Ramond field vanish.

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arXiv2010

Noncommutativity relations in type IIB theory and their supersymmetry

In the present paper we investigate noncommutativity of $D9$ and $D5$-brane world-volumes embedded in space-time of type IIB superstring theory. Boundary conditions, which preserve half of the initial supersymmetry, are treated as canonical constraints. Solving the constraints we obtain original coordinates in terms of the effective coordinates and momenta. Presence of momenta induces noncommutativity of string endpoints. We show that noncommutativity relations are connected by N=1 supersymmetry transformations and noncommutativity parameters are components of N=1 supermultiplet.

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arXiv2009

Noncommutativity in space-time extended by Liouville field

The world-sheet quantum conformal invariance can be realized in the presence of the conformal factor $F$, by inclusion of Liouville term. In the background with linear dilaton field, $Φ(x)=Φ_0+a_μx^μ$, the field $F$ becomes a new noncommutative variable. Therefore, it is natural to extend space-time with a new coordinate, $F$, in order to unify expressions for noncommutativity parameter $Θ^{ij}$ of the space-time coordinates $x^i$, with the part $Θ^i$ connecting noncommutativity between coordinates $x^i$ and $F$. In this way we solve the problems of Dp-brane noncommutativity in a more elegant way. The technical advantage uses the fact that in the extended space-time the action with dilaton field can be rewritten in dilaton free form. We use canonical method and extend its application to the derivation of boundary conditions. From requirement that Hamiltonian, as the time translation generator, has well defined derivatives in the coordinates and momenta, we obtain boundary conditions directly in the canonical form.

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arXiv2008

Type I background fields in terms of type IIB ones

We choose such boundary conditions for open IIB superstring theory which preserve N=1 SUSY. The explicite solution of the boundary conditions yields effective theory which is symmetric under world-sheet parity transformation $Ω:σ\to-σ$. We recognize effective theory as closed type I superstring theory. Its background fields,beside known $Ω$ even fields of the initial IIB theory, contain improvements quadratic in $Ω$ odd ones.

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arXiv2007

Gauge symmetries decrease the number of Dp-brane dimensions. II. Inclusion of the Liouville term

The presence of the antisymmetric background field $B_{μν}$ leads to the noncommutativity of the Dp-brane manifold, while the linear dilaton field in the form $Φ(x)=Φ_0+a_μx^μ$, causes the appearance of the commutative Dp-brane coordinate, $x_c=a_μx^μ$. In the present article we consider the case where the conformal invariance is realized by inclusion of the Liouville term. Then, the theory is conformally invariant even in the presence of the world sheet conformal factor $F$, and it depends on the new parameter, the central charge $c$. As well as in the absence of the Liouville action, for particular relations between background fields, the local gauge symmetries appear in the theory. They turn some Neumann boundary conditions into the Dirichlet ones, and decrease the number of the Dp-brane dimensions.

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arXiv2006

Gauge symmetries decrease the number of Dp-brane dimensions

It is known that the presence of antisymmetric background field $B_{μν}$ leads to noncommutativity of Dp-brane manifold. Addition of the linear dilaton field in the form $Φ(x)=Φ_0+a_μx^μ$, causes the appearance of the commutative Dp-brane coordinate $x=a_μx^μ$. In the present article we show that for some particular choices of the background fields, $a^2\equiv G^{μν}a_μa_ν=0$ and $\tilde a^2\equiv [ (G-4BG^{-1}B)^{-1}\ ]^{μν}a_μa_ν=0$, the local gauge symmetries appear in the theory. They turn some Neuman boundary conditions into the Dirichlet ones, and consequently decrease the number of the Dp-brane dimensions.

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arXiv2003

Thirring sine-Gordon relationship by canonical methods

Using the canonical method developed for anomalous theories, we present the independent rederivation of the quantum relationship between the massive Thirring and the sine-Gordon models. The same method offers the possibility to obtain the Mandelstam soliton operators as a solution of Poisson brackets "equation" for the fermionic fields. We checked the anticommutation and basic Poisson brackets relations for these composite operators. The transition from the Hamiltonian to the corresponding Lagrangian variables produces the known Mandelstam's result.

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arXiv2001

Canonical approach to 2D supersymmetric WZNW model coupled to supergravity

Starting from the known representation of the Kac-Moody algebra in terms of the coordinates and momenta, we extend it to the representation of the super Kac-Moody and super Virasoro algebras. Then we use general canonical method to construct an action invariant under local gauge symmetries, where components of the super energy-momentum tensor $L_\pm$ and $G_\pm$ play the role of the diffeomorphisms and supersymmetries generators respectively. We obtain covariant extension of WZNW theory with respect to local supersymmetry as well as explicit expressions for gauge transformations.

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arXiv2000

Canonical approach to 2D induced gravity

Using canonical method the Liouville theory has been obtained as a gravitational Wess-Zumino action of the Polyakov string. From this approach it is clear that the form of the Liouville action is the consequence of the bosonic representation of the Virasoro algebra, and that the coefficient in front of the action is proportional to the central charge and measures the quantum braking of the classical symmetry.

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arXiv1999

Canonical approach to 2D WZNW model, non-abelian bosonization and anomalies

The gauged WZNW model has been derived as an effective action, whose Poisson bracket algebra of the constraints is isomorphic to the commutator algebra of operators in quantized fermionic theory. As a consequence, the hamiltonian as well as usual lagrangian non-abelian bosonization rules have been obtained, for the chiral currents and for the chiral densities. The expression for the anomaly has been obtained as a function of the Schwinger term, using canonical methods.

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arXiv1998

Gauge connection between the WZNW system and 2D induced gravity

We introduce a consistent gauge extension of the SL(2,R) WZNW system, defined by a difference of two simple WZNW actions. By integrating out some dynamical variables in the functional integral, we show that the resulting effective theory coincides with the induced gravity in 2D. General solutions of both theories are found and related to each other.

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arXiv1998

General Solution of the WZNW System and 2D Induced Gravity in Curved Space-time

We find the general solution of the equations of motion for the WZNW system in curved space-time for arbitrary external gauge fields. Using the connection between the WZNW system for $SL(2,R)$ group and 2D induced gravity we obtain the general solution of the equations of motion for 2D induced gravity in curved space-time from that of the WZNW system. We independently presented the direct solution of 2D induced gravity equations of motion and obtain the same result.

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arXiv1998

2D induced gravity from canonically gauged WZNW system

Starting from the Kac--Moody structure of the WZNW model for SL(2,R) and using the general canonical formalism, we formulate a gauge theory invariant under local SL(2,R) x SL(2,R) and diffeomorphisms. This theory represents a gauge extension of the WZNW system, defined by a difference of two simple WZNW actions. By performing a partial gauge fixing and integrating out some dynamical variables, we prove that the resulting effective theory coincides with the induced gravity in 2D. The geometric properties of the induced gravity are obtained out of the gauge properties of the WZNW system with the help of the Dirac bracket formalism.

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arXiv1998

2D Induced Gravity as an Effective WZNW System

We introduced a dynamical system given by a difference of two simple SL(2,R) WZNW actions in 2D, and defined the related gauge theory in a consistent way. It is shown that gauge symmetry can be fixed in such a way that, after integrating out some dynamical variables in the functional integral, one obtains the induced gravity action.

hep-th↗
arXiv1996

W-Strings on Curved Backgrounds

We discuss a canonical formalism method for constructing actions describing propagation of W-strings on curved backgrounds. The method is based on the construction of a representation of the W-algebra in terms of currents made from the string coordinates and the canonically conjugate momenta. We construct such a representation for a W_3-string propagating in the background metric with one flat direction by using a simple ansatz for the W-generators where each generator is a polynomial of the canonical currents and the veilbeins. In the case of a general background we show that the simple polynomial ansatz fails, and terms containing the veilbein derivatives must be added.

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