arXiv subjects

Mohammad R. Garousi

Publications and source records attributed to Mohammad R. Garousi.

116 records · Page 7Linked to original sources

arXiv2001

Dirac-Born-Infeld action, Seiberg-Witten map, and Wilson Lines

We write the recently conjectured action for transformation of the ordinary Born-Infeld action under the Seiberg-Witten map with one open Wilson contour in a manifestly non-commutative gauge invariant form. This action contains the non-constant closed string fields, higher order derivatives of the non-commutative gauge fields through the $*_N$-product, and a Wilson operator. We extend this non-commutative $D_9$-brane action to the action for $D_p$-brane by transforming it under T-duality. Using this non-commutative $D_p$-brane action we then evaluate the linear couplings of the graviton and dilaton to the brane for arbitrary non-commutative parameters. By taking the Seiberg-Witten limit we show that they reduce exactly to the known results of the energy-momentum tensor of the non-commutative super Yang-Mills theory. We take this as an evidence that the non-commutative action in the Seiberg-Witten limit includes properly all derivative correction terms.

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arXiv2001

Transformation of the Dirac-Born-Infeld action under the Seiberg-Witten map

We explicitly evaluate the disk S-matrix elements of one closed string and an arbitrary number of open string states in the presence of a large background B-flux. From this calculation, we show that in the world-volume action of D-branes in terms of non-commutative fields, the closed string fields must be treated as functionals of the non-commutative gauge fields. We also find the generalized multiplication rule *_N between N open string fields on the world-volume of the D-brane. In particular, this result indicates that the difference between the familiar * and the *_N product is just some total derivative terms. We show that the *_N product and the dependence of the closed string fields on the non-commutative gauge fields emerge also from transforming the ordinary Dirac-Born-Infeld action(including the closed string fields) under the Seiberg-Witten map. We then conjecture a non-commutative DBI action for the transformation of the commutative DBI action under the SW map.

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arXiv2000

Tachyon couplings on non-BPS D-branes and Dirac-Born-Infeld action

By explicit evaluation of certain disk S-matrix elements in the presence of background B-flux, we find coupling of two open string tachyons to gauge field, graviton, dilaton or Kalb-Ramond antisymmetric tensor on the world-volume of a single non-BPS D$p$-brane. We then propose an extension of the abelian Dirac-Born-Infeld action which naturally reproduces these couplings in field theory. This action includes non-linearly the dynamics of the tachyon field much like the other bosonic modes of the non-BPS D$p$-brane. On the general grounds of gauge and T-duality transformations and the symmetrized trace prescription, we then extend the abelian action to non-abelian cases.

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arXiv2000

String Scattering from D-branes in Type 0 Theories

We derive fully covariant expressions for all two-point scattering amplitudes involving closed string tachyon and massless strings from Dirichlet brane in type 0 theories. The amplitude for two massless D-brane fluctuations to produce closed string tachyon is also evaluated. We then examine in detail these string scattering amplitudes in order to extract world-volume couplings of the tachyon with itself and with massless fields on a D-brane. We find that the tachyon appears as an overall coupling function in the Born-Infeld action.

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arXiv1999

Non-commutative world-volume interactions on D-brane and Dirac-Born-Infeld action

By integrating the Seiberg-Witten differential equation in a special path, we write ordinary gauge fields in terms of their non-commutative counterparts up to three non-commutative gauge fields. We then use this change of variables to write ordinary abelian Dirac-Born-Infeld action in terms of non-commutative fields. The resulting action is then compared with various low energy contact terms of world-sheet perturbative string scattering amplitudes from non-commutative D$p$-brane. We find completely agreement between the field theory and string theory results. Hence, it shows that perturbative string theory knows the solution of the Seiberg-Witten differential equation.

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arXiv1998

Superstring Scattering from D-Branes Bound States

We derive fully covariant expressions for disk scattering amplitudes of any two massless closed strings in which mixed Neumann and Dirichlet world-sheet boundary conditions are included. From the two-point amplitudes, we derive the long range background fields and verify that they correspond to D$p$-brane bound state. Also, from the scattering amplitudes, we calculate the linear coupling of closed string fields to D-brane world-volume and show that they are consistent with Born-Infeld and Chern-Simons actions in the presence of a background field.

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arXiv1996

Chiral bosonization as a Duality

We demonstrate that the technique of abelian bosonization through duality transformations can be extended to gauging anomalous symmetries. The example of a Dirac fermion theory is first illustrated. This idea is then also applied to bosonize a chiral fermion by gauging its chiral phase symmetry.

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arXiv1996

Superstring Scattering from D-Branes

We derive fully covariant expressions for all two-point scattering amplitudes of two massless closed strings from a Dirichlet $p$-brane. This construction relies on the observation that there is a simple relation between these D-brane amplitudes in type II superstring theory and four-point scattering amplitudes for type I open superstrings. From the two-point amplitudes, we derive the long range background fields for the D-branes, and verify that as expected they correspond to those of extremally charged $p$-brane solutions of the low energy effective action.

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