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Ehsan Hatefi

Publications and source records attributed to Ehsan Hatefi.

At least 37 records · Page 2Linked to original sources
arXiv2017

Highly Symmetric D-brane-Anti-D-brane Effective Actions

The entire S-matrix elements of four, five and six point functions of D-brane-anti D-brane system are explored. To deal with symmetries of string amplitudes as well as their all order $α'$ corrections we first address a four point function of one closed string Ramond-Ramond (RR) and two real tachyons on the world volume of brane-anti brane system. We then focus on symmetries of string theory as well as universal tachyon expansion to achieve both string and effective field theory of an RR and three tachyons where the complete algebraic analysis for the whole S-matrix $ $ was also revealed. Lastly, we employ all the conformal field theory techniques to $ $, working out with symmetries of theory and find out the expansion for the amplitude to be able to precisely discover all order singularity structures of D-brane-anti-D-brane effective actions of string theory. Various remarks about the so called generalized Veneziano amplitude and new string couplings are elaborated as well.

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arXiv2017

On New Bulk Singularity Structures, RR Couplings in Asymmetric Picture and Their All Order $α'$ Corrections

We have analyzed in detail four and five point functions of the string theory amplitudes, including a closed string Ramond-Ramond (RR) in an asymmetric picture and either two or three transverse scalar fields in both IIA and IIB. The complete forms of these S-matrices are derived and these asymmetric S-matrices are also compared with their own symmetric results. This leads us to explore two different kinds of bulk singularity structures as well as various new couplings in asymmetric picture of the amplitude in type II string theory. All order $α'$ higher derivative corrections to these new couplings have been discovered as well. Several remarks for these two new bulk singularity structures and for contact interactions of the S-Matrix have also been made.

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arXiv2017

On WZ and RR Couplings of BPS Branes and their all order $α'$ Corrections in IIB, IIA

We compute all three and four point couplings of BPS $D_{p}$-branes for all different nonzero $p$-values on the entire world volume and transverse directions. We start finding out all four point function supersymmetric Wess-Zumino (WZ) actions of one closed string Ramond-Ramond (RR) field with two fermions, either with the same (IIB) or different chirality (IIA) as well as their all order $α'$ corrections. The closed form of S-matrices of two closed string RR in both IIB, IIA, including their all order $α'$ corrections have also been addressed. Our results confirm that, not only the structures of $α'$ corrections but also their coefficients of IIB are quite different from their IIA ones. The S-matrix of an RR and two gauge (scalar) fields and their all order corrections in antisymmetric picture of RR have been carried out as well. Various remarks on the restricted Bianchi identities as well as all order $α'$ corrections to all different supersymmetric WZ couplings in both type IIA and IIB superstring theory are also released. Lastly, different singularity structures as well as all order contact terms for all non-vanishing traces in type II have also been constructed.

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arXiv2017

Remarks on Non-BPS String Amplitudes and Their All Order $α'$ Contact Interactions in IIB, IIA

We explore the entire form of S-Matrix elements of a potential $C_{n-1}$ Ramond-Ramond (RR) form field, a tachyon and two transverse scalar fields on both world volume and transverse directions of type IIB and IIA superstring theories. Apart from $ $ the other scattering amplitude, namely $ $ is also revealed. We then start to compare all singularity structures of symmetric and asymmetric analysis, generating all infinite singularity structures as well as all order $α'$ contact interactions on the whole directions. This leads to deriving various new contact terms and several new restricted Bianchi identities in both type IIB and IIA. It is also shown that just some of the new couplings of type IIB (IIA) string theory can be re-verified in an Effective Field Theory (EFT) by pull-back of branes. To construct the rest of S-matrix elements one needs to first derive restricted world volume (or bulk) Bianchi identities and then discover new EFT couplings in both type IIB and IIA. Finally the presence of commutator of scalar fields inside the exponential of Wess-Zumino action for non-BPS branes has been confirmed as well.

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arXiv2016

On Bulk Singularity Structures and all order $α'$ Contact Terms of BPS String Amplitudes

The entire form of the amplitude of three SYM ( involving two transverse scalar fields, a gauge field) and a potential $C_{n-1}$ Ramond-Ramond (RR) form field is found out. We first derive $ $ and then start constructing an infinite number of $t,s$ channel bulk singularity structures by means of all order $α'$ corrections to pull-back of brane in an Effective Field Theory (EFT). Due to presence of the complete form of S-matrix, several new contact interactions as well as new couplings are explored. It is also shown that these couplings can be verified at the level of EFT by either the combinations of Myers terms, pull-back, Taylor expanded of scalar fields or the mixed combination of the couplings of this paper as well as employed Bianchi identities. For the first time, we also derive the algebraic and the complete form of the integrations for some arbitrary combinations of Mandelstam variables and for the most general case $\int d^2z |1-z|^{a} |z|^{b} (z - \bar{z})^{c} (z + \bar{z})^{3}$ on upper half plane as well.

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arXiv2016

On RR Couplings and Bulk Singularity Structures of Non-BPS Branes

We compute the five point world sheet scattering amplitude of a symmetric closed string Ramond-Ramond , a transverse scalar field, a world volume gauge field and a real tachyon in both world volume and transverse directions of brane in type IIA and IIB superstring theory. We provide the complete analysis of $ $ S-matrix and show that both $u'=u+\frac{1}{4}$ and $t$ channel bulk singularity structures can also be examined by this S-matrix. Various remarks about new restricted Bianchi identities on world volume for the other pictures have also been made.

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arXiv2016

On D-brane-Anti D-brane Effective actions and their all order Bulk Singularity Structures

All four point functions of brane anti brane system including their correct all order $α'$ corrections have been addressed. All five point functions of one closed string Ramond-Ramond (RR), two real tachyons and either one gauge field or the scalar field in both symmetric and asymmetric pictures have also been explored. The entire analysis of $ $ is carried out. Not only does it fix the vertex operator of RR in asymmetric picture and in higher point functions of string theory amplitudes but also it confirms the fact that there is no issue of picture dependence of the mixed closed RR, gauge fields, tachyons and fermion fields in all symmetric or anti symmetric ones. We compute $ $ S-matrix in the presence of a transverse scalar field, two real tachyons and that reveals two different kinds of bulk singularity structures, involving an infinite number of $u$- channel gauge field and $(u+s'+t')$- channel scalar bulk poles. In order to produce all those bulk singularity structures, we define various couplings at the level of the effective field theory that involve the mixing term of Chern-Simons coupling (with C-potential field) and a covariant derivative of the scalar field that comes from the pull-back of brane. Eventually we explore their all order $α'$ corrections in the presence of brane anti brane system where various remarks will be also pointed out.

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arXiv2015

On RR Couplings, Singularity Structures and all order $α'$ contact interactions to BPS String Amplitudes

We evaluate five point world-sheet string theory amplitudes of one transverse scalar field, two world volume gauge fields ( and two transverse scalars, a gauge field) in the presence of a closed string Ramond-Ramond vertex operator in its symmetric picture. We carry out all the entire S-matrix elements of five point mixed RR-scalars/gauge fields $ $, $ $, $ $ and $ $ in detail and start comparing all order $α'$ contact interactions and singularities in both transverse and world volume directions. We explore the presence of various new couplings in string theory effective actions and find out their all order $α'$ higher derivative corrections in both type IIA and IIB. Ultimately we make various remarks for the singularities and contact terms whose RR momenta are embedded in transverse directions. $α'$ corrections to some of Myers terms are also addressed.

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arXiv2015

Remarks on the mixed Ramond -Ramond, open string scattering amplitudes of BPS, non-BPS and brane-anti brane

From the world-sheet point of view we compute three, four and five point BPS and non-BPS scattering amplitudes of type IIA and IIB superstring theory. All these the mixed S-matrix elements including a closed string Ramond-Ramond (RR) in the bulk and a scalar/gauge or tachyons with their all different pictures ( including RR in asymmetric and symmetric pictures) have been carried out. We have also shown that in asymmetric pictures various equations must be kept fixed. More importantly, by direct calculations on upper half plane, it is realized that some of the equations (that must be true) for BPS branes can not be necessarily applied to non-BPS amplitudes. We also derive the S-Matrix elements of $ $ and clarify the fact that in the presence of the scalar field and RR, the terms carrying momentum of RR in transverse directions play important role in the entire form of the S-matrix and their presence is needed in order to have gauge invariance for the entire S-matrix elements of type IIA (IIB) superstring theory.

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arXiv2014

SYM, Chern-Simons, Wess-Zumino Couplings and their higher derivative corrections in IIA Superstring theory

We find the entire form of the amplitude of two fermion strings (with different chirality), a massless scalar field and one closed string Ramond-Ramond (RR) in IIA superstring theory which is different from its IIB one. We make use of a very particular gauge fixing and explore several new couplings in IIA. All infinite $u$- channel scalar poles and $t,s$- channel fermion poles are also constructed. We find new form of higher derivative corrections to two fermion two scalar couplings and show that the first simple $(s+t+u)-$ channel scalar pole for $p+2=n$ case can be obtained by having new higher derivative corrections to SYM couplings at third order of $α'$. We find that the general structure and the coefficients of higher derivative corrections to two fermion two scalar couplings are completely different from the derived $α'$ higher derivative corrections of type IIB.

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arXiv2014

More on Ramond-Ramond, SYM, WZ couplings and their corrections in IIA

We obtain the closed form of the correlation function of one current and four spin operators (with different chiralities ) in type IIA superstring theory. The complete form of the S-matrix of one gauge , two fermions (with different chiralities) and one closed string Ramond-Ramond for all order $α'$ type IIA has been explored. Moreover, we make use of a different gauge fixing to be able to find out all the closed forms of $ $ correlators. An infinite number of $t,s-$channel fermion poles of this S-matrix in the field theory of IIA is generated. Unlike the the closed form of the correlators of the same amplitude of IIB, for various $p,n$ cases in type IIA we do have different double poles in $t,(t+s+u)$ and in $s,(t+s+u)$ channels and we produced them. We also find new Wess-Zumino couplings of IIA with their third order $α' $ corrections as well as a new form of higher derivative corrections (with different coefficient from its IIB one ) to SYM couplings at third order of $α' $. Using them, we are able to produce a $(t+s+u)$ channel scalar pole of the $ $ amplitude for $p+2=n$ case. Finally we make some comments on $α'$ corrections to IIA Superstring theory.

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arXiv2014

SuperYang-Mills, Chern-Simons couplings and their all order $α'$ corrections in IIB superstring theory

We explore the closed form of the correlation function of four spin operators (including one closed string Ramond-Ramond (RR) and two open string fermions) and one current in ten dimensions, to be able to find the complete and the closed form of the amplitude of one closed string Ramond-Ramond, one gauge field and two fermionic strings (with the same chirality) to all orders in $α'$ in IIB superstring theory. In particular we use a special gauge fixing to the amplitude and apply fermions' equations of motion to $ $ correlator. String amplitude induced that neither there should be any $u-$channel gauge poles for $p=n+2$ case nor there are couplings between two fermions and two gauge fields for $p=n$ case in the field theory of type IIB. All infinite $u-$ channel scalar poles and $t,s-$channel fermion poles of the string amplitude are useful in discovering new couplings of type IIB. More specifically, by making use of the SYM couplings of one scalar, one gauge and two fermions and their all order $α'$ higher derivative corrections, we are able to exactly produce all infinite $(s+t+u)-$ channel scalar poles of $ $ .

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arXiv2014

Closed string Ramond-Ramond proposed higher derivative interactions on fermionic amplitudes in IIB

The complete form of the amplitude of one closed string Ramond-Ramond (RR), two fermionic strings and one scalar field in IIB superstring theory has been computed in detail. Deriving $ $ by using suitable gauge fixing, we discover some new vertices and their higher derivative corrections. We investigate both infinite gauge and scalar $u-$channel poles of this amplitude. In particular, by using the fact that the kinetic term of fermion fields has no correction, employing Born-Infeld action, the Wess-Zumino terms and their higher derivative corrections, we discover all infinite $t,s-$channel fermion poles. The couplings between one RR and two fermions and all their infinite higher derivative corrections have been explored. In order to look for all infinite $(s+t+u)-$ channel scalar/gauge poles for $p+2=n,p=n$ cases, we obtain the couplings between two fermions-two scalars and two fermions, one scalar and one gauge field as well as all their infinite higher derivative corrections in type IIB. Specifically we make various comments based on arXiv:1205.5079 in favor of universality conjecture for all order higher derivative corrections (with or without low energy expansion) and the relation of open/closed string that is responsible for all superstring scattering amplitudes in IIA,IIB.

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arXiv2013

Selection Rules and RR Couplings on Non-BPS Branes

We compute three and four point functions of the non-BPS scattering amplitudes, including a closed string Ramond-Ramond, gauge/scalar and tachyon in type IIA (IIB) superstring theories. We then discover a unique expansion for tachyon amplitudes in both non-BPS and D-brane anti D-brane formalisms. Based on remarks on Chan-Paton factors and arXiv:1304.3711, we propose selection rules for all non-BPS scattering amplitudes of type II superstring theory. These selection rules, rule out various non-BPS higher point correlation functions of the string theory.

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arXiv2013

On D-brane anti D-brane effective actions and their corrections to all orders in alpha-prime

Based on a four point function, the S-matrix elements at disk level of the scattering amplitude of one closed string Ramond-Ramond field ($C$), two tachyons and one scalar field, we find out new couplings in brane anti brane effective actions for $p=n,p+2=n$ cases. Using the infinite corrections of the vertex of one RR, one gauge and one scalar field and applying the correct expansion, it is investigated in detail how we produce the infinite gauge poles of the amplitude for $p = n$ case. By discovering new higher derivative corrections of two tachyon-two scalar couplings in brane anti brane systems to all orders in $α'$, we also obtain the infinite scalar poles in $t'+s'+u$-channel in field theory. Working with the complete form of the amplitude with the closed form of the expansion and comparing all the infinite contact terms of this amplitude, we derive several new Wess-Zumino couplings with all their infinite higher derivative corrections in the world volume of brane anti brane systems. In particular, in producing all the infinite scalar poles of $ $, one has to consider the fact that scalar 's vertex operator in $(-1)$-picture must carry the internal $σ_3$ Chan-Paton matrix. The symmetric trace effective action has a non-zero coupling between $Dϕ^{(1)i}$ and $Dϕ^{(2)}_i$ while this coupling does not exist in ordinary trace effective action.

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arXiv2013

All order $α'$ higher derivative corrections to non-BPS branes of type IIB Super string theory

By dealing with the evaluation of string theory correlators of $ $, the complete and closed form of the amplitude of two fermion fields, one tachyon and one closed string Ramond-Ramond field in type IIB superstring theory is found. Specifically by comparing infinite tachyon poles in field theory amplitude with infinite tachyon poles of the S-matrix of string amplitude (for $p+1=n$ case), all the infinite higher derivative corrections of two tachyons and two fermions (in type IIB) to all orders of $α'$ have been discovered. Using these new couplings, we are able to produce infinite $t'+s'+u$-channel tachyon poles of string theory in field theory. Due to internal degrees of freedom of fermions and tachyon (Chan-Paton factors) we comment that, neither there should be single $s,t-$channel fermion (tachyon pole) nor their infinite poles. Due to internal CP factor we also discover that there is no coupling between two closed string Ramond-Ramond (RR) field and one tachyon in type II super string theory. Taking into account the fact that the kinetic terms of fermions, gauge, scalar fields and tachyons do not obtain any higher derivative corrections, and due to their CP factors, string theory amplitude dictates us there should not be any double poles in the amplitude of one RR, two fermions and one tachyon.

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arXiv2013

On higher derivative corrections to Wess-Zumino and Tachyonic actions in type II super string theory

We evaluate in detail the string scattering amplitude to compute different interactions of two massless scalars, one tachyon and one closed string Ramond-Ramond field in type II super string theory. In particular we find two scalar field and two tachyon couplings to all orders of $α'$ up to on-shell ambiguity. We then obtain the momentum expansion of this amplitude and apply this infinite number of couplings to actually check that the infinite number of tachyon poles of S-matrix element of this amplitude for the $p=n$ case (where $p$ is the spatial dimension of a D$_p$-brane and $n$ is the rank of a Ramond-Ramond field strength) to all orders of $α'$ is precisely equal to the infinite number of tachyon poles of the field theory. In addition to confirming the couplings of closed string Ramond-Ramond field to the world-volume gauge field and scalar fields including commutators, we also propose an extension of the Wess-Zumino action which naturally reproduces these new couplings in field theory such that they could be confirmed with direct S-matrix computations. Finally we show that the infinite number of massless poles and contact terms of this amplitude for the $p=n+1$ case can be reproduced by Chern-Simons, higher derivative corrections of the Wess-Zumino and symmetrized trace tachyon DBI actions.

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