RR Couplings Research Articles

Comparison of QT interval variability of coronary patients without myocardial infarction with that of patients with old myocardial infarction

BackgroundThe significant association of myocardial ischemia with elevated QT interval variability (QTV) has been reported in myocardial infarction (MI) patients. However, the influence of the time course of MI on QTV has not been investigated systematically. MethodShort-term QT and RR interval time series were constructed from the 5 min electrocardiograms of 49 coronary patients without MI and 26 patients with old MI (OMI). The QTV, heart rate variability (HRV), and QT–RR coupling of the two groups were analyzed using various time series analysis tools in the time- and frequency-domains, as well as nonlinear dynamics. ResultsNearly all of the tested QTV indices for coronary patients with OMI were higher than those for patients without MI. However, no significant differences were found between the two groups in any of the variables employed to assess the HRV and QT–RR coupling. All of the markers that showed statistical significances in univariate analyses still possessed the capabilities of distinguishing between the two groups even after adjusting for studied baseline characteristics, including the coronary atherosclerotic burden. ConclusionsThe results suggested that the QTV increased in coronary patients with OMI compared to those without MI, which might reflect the influence of post-MI remodeling on the beat-to-beat temporal variability of ventricular repolarization. The non-significant differences in the HRV and QT–RR couplings could indicate that there were no differences in the modulation of the autonomic nervous system and interaction of QT with the RR intervals between the two groups.

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 $<C^{-1} \phi^0 A^0 T ^{-1}>$ 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.

Puzzles of η-deformed AdS5 × S5

We derive the part of the Lagrangian for the sigma model on the eta-deformed AdS_5 x S^5 space which is quadratic in fermions and has the full dependence on bosons. We then show that there exists a field redefinition which brings the corresponding Lagrangian to the standard form of type IIB Green-Schwarz superstring. Reading off the corresponding RR couplings, we observe that they fail to satisfy the supergravity equations of motion, despite the presence of kappa-symmetry. However, in a special scaling limit our solution reproduces the supergravity background found by Maldacena and Russo. Further, using the fermionic Lagrangian, we compute a number of new matrix elements of the tree level world-sheet scattering matrix. We then show that after a unitary transformation on the basis of two-particle states which is not one-particle factorisable, the corresponding T-matrix factorises into two equivalent parts. Each part satisfies the classical Yang-Baxter equation and coincides with the large tension limit of the q-deformed S-matrix.

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 <C −1 ϕ 0 A −1 A 0>, <C −1 ϕ −1 A 0 A 0>, <C −1 A 0 ϕ −1 ϕ 0> and <C −1 A −1 ϕ 0 ϕ 0> 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.

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.

S-duality of D-brane action at order [formula omitted

Using the compatibility of the DBI and the Chern–Simons actions with the T-duality transformations, the curvature corrections to these actions have been recently extended to include the quadratic B-field couplings at order O(α′2). In this paper, we use the compatibility of the couplings on D3-brane with the S-duality to find the nonlinear RR couplings at order O(α′2). We confirm the quadratic RR couplings in the DBI part with the disk-level scattering amplitude. Using the modular functions that appear in the curvature corrections, we then write the results in SL(2,Z) invariant form.

On RR couplings on D-branes at order O(α′2)

Recently, it has been found that there are couplings of the RR field strength F (p) and the B-field strength H on the world volume of Dp-branes at order $ \mathcal{O}\left( {{\alpha^{{\prime}2}}} \right) $ . These couplings which have both world-volume and transverse indices, are invariant under the linear T-duality transformations. Consistency with the nonlinear T-duality indicates that the RR field strength F (p) in these couplings should be replaced by $ {\mathcal{F}^{(p)}} = d{\mathcal{C}^{\left( {p - 1} \right)}} $ where $ \mathcal{C} = {e^B}C $ . This replacement, however, produces some non-gauge invariant terms. On the other hand, the nonlinear terms are invariant under the linear T-duality transformations at the level of two B-fields. This allows one to remove some of the nonlinear terms in $ {\mathcal{F}^{(p)}} $ . We fix this by comparing the nonlinear couplings with the S-matrix element of one RR and two NSNS vertex operators. Our results indicate that in the expansion of $ {\mathcal{F}^{(p)}} $ one should keep only the B-field gauge invariant terms, e.g., B ∧ dC (p−3) where both indices of B-field lie along the brane. Moreover, in this case one should replace B with B + 2πα′f to have the B-field gauge invariance.

Exact Seiberg–Witten map, induced gravity and topological invariants in non-commutative field theories

We revisit the exact Seiberg–Witten (SW) map on Dirac–Born–Infeld actions, making a connection with the deformation quantization scheme. The picture on field dependent induced gravity from non-commutativity becomes more transparent in the context of deformation quantization. We also find an exact SW map for an adjoint scalar field, consistent with that deduced from RR couplings of unstable non-BPS D-branes. The dual description via the exact SW map can again be interpreted as the ordinary field theory coupling to gravity induced by gauge fields. Using the exact SW maps, we further discuss several aspects of topological invariants in non-commutative (NC) gauge theory. Especially, it is shown that the K-theory class on NC instantons is mapped to the usual second Chern class via exact SW map and it leads to an exact SW map between commutative and NC Chern–Simons terms.

New Standard Model Vacua from Intersecting Branes

We construct new D6-brane model vacua (non-supersymmetric) that have at low energy exactly the standard model spectrum (with right handed neutrinos). The minimal version of these models requires five stacks of branes. and the construction is based on D6-branes intersecting at angles in $D = 4$ type toroidal orientifolds of type I strings. Three U(1)'s become massive through their couplings to RR couplings and from the two surviving anomaly free U(1)'s, one is the standard model hypercharge generator while the extra anomaly free U(1) could be broken from its non-zero couplings to RR fields and also by triggering a vev to previously massive particles. We suggest that extra massless U(1)'s should be broken by requiring some intersection to respect N=1 supersymmetry thus supporting the appearance of massless charged singlets at the supersymmetric intersection. Proton is stable as baryon number is gauged and its anomalies are cancelled through a generalized Green-Schwarz mechanism. Neutrinos are of Dirac type with small masses, as in the four stack standard models of hep-th/0105155, as a result of the existence of a similar PQ like-symmetry. The models are unique in the sense that they predict the existence of only one supersymmetric particle, the superpartner of $\nu_R$.

On unification of RR couplings

We consider the couplings of RR fields with open string sector for $Dp$-${\overline{Dp}}$ backgrounds of various $p$. Proposed approach, based on the approximation of the open string algebra by the algebra of differential operators, provides the unified description of these couplings and their interrelations.

Gauge-invariant couplings of noncommutative branes to Ramond-Ramond backgrounds

We derive the couplings of noncommutative D-branes to spatially varying Ramond-Ramond fields, extending our earlier results in hep-th/0009101. These couplings are expressed in terms of *n products of operators involving open Wilson lines. Equivalence of the noncommutative to the commutative couplings implies interesting identities as well as an expression for the Seiberg-Witten map that was previously conjectured. We generalise our couplings to include transverse scalars, thereby obtaining a Seiberg-Witten map relating commutative and noncommutative descriptions of these scalars. RR couplings for unstable non-BPS branes are also proposed.

A note on the torsion dependence of D-brane RR couplings

The dependence on the torsion H= db of the Wess–Zumino couplings of D-branes that are trivially embedded in space–time is studied. We show that even in this simple set-up some torsion components can be turned on, with a non-trivial effect on the RR couplings. In the special cases in which either the tangent or the normal bundle are trivial, the torsion dependence amounts to substitute the standard curvature with its generalization in the presence of torsion, in the usual couplings involving the roof genus Â.