2,625 research outputs found
The twisted open string partition function and Yukawa couplings
We use the operator formalism to derive the bosonic contribution to the
twisted open string partition function in toroidal compactifications. This
amplitude describes, for instance, the planar interaction between g+1
magnetized or intersecting D-branes. We write the result both in the closed and
in the open string channel in terms of Prym differentials on the appropriate
Riemann surface. Then we focus on the g=2 case for a 2-torus. By factorizing
the twisted partition function in the open string channel we obtain an explicit
expression for the 3-twist field correlator, which is the main ingredient in
the computation of Yukawa couplings in D-brane phenomenological models. This
provides an alternative method for computing these couplings that does not rely
on the stress-energy tensor technique.Comment: 32 pages, 5 figures, Latex; v2: typos correcte
New twist field couplings from the partition function for multiply wrapped D-branes
We consider toroidal compactifications of bosonic string theory with
particular regard to the phases (cocycles) necessary for a consistent
definition of the vertex operators, the boundary states and the T-duality
rules. We use these ingredients to compute the planar multi-loop partition
function describing the interaction among magnetized or intersecting D-branes,
also in presence of open string moduli. It turns out that unitarity in the open
string channel crucially depends on the presence of the cocycles. We then focus
on the 2-loop case and study the degeneration limit where this partition
function is directly related to the tree-level 3-point correlators between
twist fields. These correlators represent the main ingredient in the
computation of Yukawa couplings and other terms in the effective action for
D-brane phenomenological models. By factorizing the 2-loop partition function
we are able to compute the 3-point couplings for abelian twist fields on
generic non-factorized tori, thus generalizing previous expressions valid for
the 2-torus.Comment: 36 pages, 1 figure; v2: typos corrected, proof in the Appendix
improve
Gluons and the eta' nucleon coupling constant
We derive the effective chiral Lagrangian for low energy eta--nucleon and
eta'--nucleon interactions and show that gluonic degrees of freedom, via the
axial anomaly, induce a contact term in the pp -> pp eta and pp -> pp eta'
reactions. We then discuss the consequences for the extraction of g_{eta'NN}
from experimental data.Comment: 10 pages, LaTe
N=1 Matter from Fractional Branes
We study a bound state of fractional D3-branes localized inside the
world-volume of fractional D7-branes on the orbifold C^3/Z_2 x Z_2. We
determine the open string spectrum that leads to N=1 U(N1)xU(N2)xU(N3)xU(N4)
gauge theory with matter having the number of D7-branes as a flavor index. We
derive the linearized boundary action of the D7-brane on this orbifold using
the boundary state formalism and we discuss the tadpole cancellation. After
computing the asymptotic expression of the supergravity solution the anomalies
of the gauge theory are reproduced.Comment: LaTeX 20 pages, 1 figure, small changes and references adde
Full QCD calculation of neutron electric dipole moment with the external electric field method
We have calculated the neutron electric dipole moment (NEDM) in the presence
of the CP violating term in lattice QCD with 2-flavor dynamical clover
quarks, using the external electric field method. Accumulating a large number
of statistics by the averages over 16 different source points and over forward
and backward nucleon propagators, we have obtained non-zero signals of neutron
and proton EDM beyond one standard deviation at each quark mass in full QCD. We
have investigated the quark mass dependence of nucleon EDM in full QCD, and
have found that nucleon EDM in full QCD does not decrease toward the chiral
limit, as opposed to the theoretical expectation. We briefly discuss possible
reasons for this behavior.Comment: 27 pages, 15 figures, 2 tables, reference added, tyops corrected,
published versio
Wrapped Magnetized Branes: Two Alternative Descriptions?
We discuss two inequivalent ways for describing magnetized D-branes wrapped N
times on a torus T^2. The first one is based on a non-abelian gauge bundle
U(N), while the second one is obtained by means of a Narain T-duality
transformation acting on a theory with non-magnetized branes. We construct in
both descriptions the boundary state and the open string vertices and show that
they give rise to different string amplitudes. In particular, the description
based on the gauge bundle has open string vertex operators with momentum
dependent Chan-Paton factors.Comment: 60 pages, LaTe
Effect of Progressive Integration of On-Board Systems Design Discipline in an MDA Framework for Aircraft Design with Different Level of Systems Electrification
The on-board design discipline is sometimes ignored during the first aircraft design iterations. It might be understandable when a single on-board system architecture is considered, especially when a conventional architecture is selected. However, seeing the trend towards systems electrification, multiple architectures can be defined and each one should be evaluated during the first tradeoff studies. In this way, the systems design discipline should be integrated from the first design iterations. This paper deals with a progressive integration of the discipline to examine the partial or total effect of the systems design inside an MDA workflow. The study is carried out from a systems design perspective, analyzing the effect of electrification on aircraft design, with different MDA workflow arrangements. Starting from a non-iterative systems design, other disciplines such as aircraft performance, engine design, and aircraft synthesis are gradually added, increasing the sensibility of the aircraft design to the different systems architectures. The results show an error of 40% in on-board systems assessment when the discipline is not fully integrated. Finally, using the work-flow which allows for greater integration, interesting differences can be noted when comparing systems with different levels of electrification. A possible mass saving of 2.6% of aircraft MTOM can be reached by properly selecting the systems technologies used
The Non-Perturbative SUSY Yang-Mills Theory from Semiclassical Absorption of Supergravity by Wrapped D Branes
The imaginary part of the two point functions of the superconformal anomalous
currents are extracted from the cross-sections of semiclassical absorption of
dilaton, RR-2 form and gravitino by the wrapped D5 branes. From the central
terms of the two point functions anomalous Ward identity is established which
relates the exact pre-potential of the SUSY Yang-Mills theory with
the vacuum expectation value of the anomaly multiplet. From the Ward identity,
WDVV (Witten-Dijkgraaf-Verlinde-Verlinde) equation can be derived which is
solved for the exact pre-potential.Comment: 11 pages, late
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