arXiv subjects

Davoud Kamani

Publications and source records attributed to Davoud Kamani.

65 records · Page 4Linked to original sources

arXiv2003

PP-Wave Strings from Membrane and from String in the Spacetime with Two Time Directions

In this paper we obtain strings that propagate in the quantized pp-wave backgrounds. We can obtain these strings from the solutions of membrane. The other way is the propagation of a massless string in a spacetime with two time dimensions. This string sweeps a worldvolume, which enables us to obtain other strings in the quantized pp-wave backgrounds in the spacetime with one time direction. The associated algebras and Hamiltonians of these massive strings will be studied.

hep-th↗

arXiv2002

Closed Superstring in Noncommutative Compact Spacetime

In this paper we study the effects of noncommutativity on a closed superstring propagating in the spacetime that is compactified on tori. The effects of compactification and noncommutativity appear in the momentum, quantization, supercurrent, super-conformal generators and in the boundary state of the closed superstring emitted from a D$_p$-brane with the NS$\otimes$NS background $B$-field.

hep-th↗

arXiv2002

Noncommutativity Parameter As a Field on the String Worldsheet

We consider the noncommutativity parameter of the space-time as a bosonic worldsheet field. By finding a fermionic super-partner for it, we can find star products between the boson-boson, boson-fermion and fermion-fermion fields of superstring worldsheet and also between superfields of the worldsheet superspace. We find a two dimensional action for the noncommutativity parameter and its fermionic partner. We discuss the symmetries of this action.

hep-th↗

arXiv2002

Noncommutative Superstring Worldsheet

In this paper we consider the worldsheet of superstring as a noncommutative space. Some additional terms can be added to the superstring action, such that for ordinary worldsheet they are zero. Expansion of this extended action up to the first order of the noncommutativity parameter, leads to the new supersymmetric action for string. For the closed superstring, we obtain the boundary state that describes a brane. From the open string point of view, the new boundary conditions on the worldsheet bosons, generalize the noncommutativity of spacetime. Finally, we suggest some definitions for the noncommutativity parameter of superstring worldsheet.

hep-th↗

arXiv2002

Space-Time Symmetries, T-Duality and Gauge Theory

In this paper we study U(1) gauge transformations on the space-time coordinates and on the background fields $g_{μν}$ and $ϕ$. For some special gauge functions, gauged coordinates and gauged U(1) field are equivalent to the rotated coordinates and rotated gauge field. We find gauge transformations that are symmetries of the string action. Also we obtain general $T$-duality transformations for the background fields. For special background fields this duality is equivalent to a gauge transformation.

hep-th↗

arXiv2001

Noncommutativity and the Motion of D$_p$-brane along Itself

We consider open strings attached to a moving D$_p$-brane with motion along itself, in the presence of the backgrounds $B_{μν}$-field and a U(1) gauge field $A_α$. The effects of the motion of the brane on the open string propagator and on the open string variables are studied. We observe that some free parameters appear in the open string variables and in the propagator of it.

hep-th↗

arXiv2001

T-duality and Noncommutative DBI Action

In this article we study the noncommutative description of the DBI Lagrangian and its T-dual counterpart. We restrict the freedoms of the noncommutativity parameters of these Lagrangians. Therefore the noncommutativity parameter, the effective metric, the effective coupling constant of the string and the extra modulus ${\tilde Φ}$ of the effective T-dual theory, can be expressed in terms of the closed string variables $g$, $B$, $g_s$ and the noncommutativity parameter of the effective theory of open string.

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arXiv2001

General Target Space Duality and Its Effects on D-branes

We study a special combination of the compact directions of the spacetime (compactified on tori) and the worldsheet parity transformed of these directions. The transformations that change the compact part of the spacetime to this combination, are more general than the T-duality transformations. Many properties of this combination and also of the corresponding worldsheet fermions are studied. By using the boundary state formalism, we study the effects of the above transformations to D-branes. For the special cases the resulted branes reduce to the known mixed branes, or reduce to the modified mixed branes.

hep-th↗

arXiv2000

T-Duality and Mixed Branes

In this article the action of T-duality on a mixed brane is studied in the boundary state formalism. We also obtain a two dimensional mixed brane with non-zero electric and magnetic fields, from a D$_1$-brane.

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arXiv1999

Moving Mixed Branes in Compact Spacetime

In this article we present a general description of two moving branes in presence of the $B_{μν}$ field and gauge fields $A^{(1)}_{α_1}$ and $A^{(2)}_{α_2}$ on them, in spacetime in which some of its directions are compact on tori. Some examples are considered to elucidate this general description. Also contribution of the massless states to the interaction is extracted. Boundary state formalism is a useful tool for these considerations.

hep-th↗

arXiv1999

Mixed Branes at Angle in Compact Spacetime

In this article the interaction of branes at angles with respect to each other with non-zero internal gauge fields are calculated by construction of the boundary states in spacetime in which some of its directions are compact on tori. The interaction depends on both angle and fields.

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