scholarly journals Three Point Tree Level Amplitude in Superstring Theory

2011 ◽  
Vol 216 (1) ◽  
pp. 234-238 ◽  
Author(s):  
Ehsan Hatefi
Keyword(s):  
Tree Level ◽  
Superstring Theory ◽  
Tree Level Amplitude

scholarly journals Generalized two-point tree-level amplitude j f → j′ f′ in a magnetized medium

2015 ◽  
Vol 30 (11) ◽  
pp. 1550049 ◽  
Author(s):  
A. V. Kuznetsov ◽  
D. A. Rumyantsev ◽  
D. M. Shlenev
Keyword(s):  
Magnetic Field ◽  
Axial Vector ◽  
Field Operator ◽  
Coherent Scattering ◽  
Tree Level ◽  
Tree Level Amplitude ◽  
Photoproduction Process ◽  
Arbitrary Strength ◽  
Neutrino Emissivity ◽  
A Current

The tree-level two-point amplitudes for the transitions j f → j′ f′, where f is a fermion and j is a generalized current, in a constant uniform magnetic field of an arbitrary strength and in charged fermion plasma, for the j f f interaction vertices of the scalar, pseudoscalar, vector and axial-vector types have been calculated. The generalized current j could mean the field operator of a boson, or a current consisting of fermions, e.g. the neutrino current. The particular cases of a very strong magnetic field, and of the coherent scattering off the real fermions without change of their states (the "forward" scattering) have been analyzed. The contribution of the neutrino photoproduction process, [Formula: see text], to the neutrino emissivity has been calculated with taking account of a possible resonance on the virtual electron.

INFLATION FROM THE SUPERSTRING VACUUM

2009 ◽  
Vol 24 (20n21) ◽  
pp. 4021-4037
Author(s):  
M. D. POLLOCK
Keyword(s):  
Background Radiation ◽  
Physical Space ◽  
Reduction Process ◽  
Tree Level ◽  
Internal Space ◽  
De Sitter ◽  
Superstring Theory ◽  
Higher Derivative ◽  
Effective Lagrangian ◽  
Microwave Background Radiation

Quartic higher-derivative gravitational terms in the effective Lagrangian of the heterotic superstring theory renormalize the bare, four-dimensional gravitational coupling [Formula: see text], due to the reduction process [Formula: see text], according to the formula [Formula: see text], where A r and B r are the moduli for the physical space gij(xk) and internal space [Formula: see text], respectively. The Euler characteristic [Formula: see text] is negative for a three-generation Calabi–Yau manifold, and therefore both the additional terms, of tree-level and one-loop origin, produce a decrease in κ-2, which changes sign when κ-2 = 0. The corresponding tree-level critical point is [Formula: see text], if we set [Formula: see text] and λ = 15π2, for compactification onto a torus. Values [Formula: see text] yield the anti-gravity region κ-2 < 0, which is analytically accessible from the normal gravity region κ-2 > 0. The only non-singular, vacuum minimum of the potential [Formula: see text] is located at the point [Formula: see text], where [Formula: see text], the quadratic trace anomaly [Formula: see text] dominates over [Formula: see text], and a phase of de Sitter expansion may occur, as first envisaged by Starobinsky, in approximate agreement with the constraint due to the effect of gravitational waves upon the anisotropy of the cosmic microwave background radiation. There is no non-singular minimum of the potential [Formula: see text].

scholarly journals AN EXTENDED N=1 FERMIONIC SUPERCURRENT AND ITS ASSOCIATED N=2 SUPERCONFORMAL ALGEBRA

1995 ◽  
Vol 10 (38) ◽  
pp. 2967-2977
Author(s):  
DAVID M. PIERCE
Keyword(s):  
Superconformal Algebra ◽  
Tree Level ◽  
Intermediate Step ◽  
Superstring Theory ◽  
Massless Fermions

An extended free fermionic construction of the internal N=1 worldsheet supercurrent for four-dimensional superstring theory is given. We show how it can describe theories with massless fermions, and we discuss the corresponding N=2 superconformal algebra. As an intermediate step, we show that an internal N=2 global superconformal invariance occurs in any superstring theory with massless fermions at tree level. To demonstrate this fact, we give the N=2 supercurrents for a model with N=1 spacetime supersymmetry and a model without spacetime supersymmetry.

scholarly journals Constraints on Tree-Level Higher Order Gravitational Couplings in Superstring Theory

2011 ◽  
Vol 106 (11) ◽  
Author(s):  
Stephan Stieberger
Keyword(s):  
Higher Order ◽  
Tree Level ◽  
Superstring Theory

scholarly journals NONCOMMUTATIVE N = 2 p - p′ SYSTEM

2002 ◽  
Vol 17 (08) ◽  
pp. 1117-1135
Author(s):  
AALOK MISRA
Keyword(s):  
Field Theory ◽  
Low Energy ◽  
Tree Level ◽  
P System ◽  
Star Products ◽  
Energy Limit ◽  
Point Function ◽  
Tree Level Amplitude ◽  
Complex Dimensions ◽  
Open Sector

We analyze several open and mixed sector tree-level amplitudes in N = 2 p - p′ systems with a constant magnetic B turned on. The three-point function vanishes on-shell. The four-point function, in the Seiberg–Witten (SW) low energy limit,2 is local, indicating the possible topological nature of the theory (in the SW low energy limit) and the possible relation between noncommutativeN = 2 p - p′system in two complex dimensions and in the SW limit, and (non)commutativeN = 2 p′ - p′system in two real dimensions. We discuss three extreme noncommutativity limits (after having taken the Seiberg–Witten low energy limit) of the mixed three-point function, and get two kinds of commutative nonassociative generalized star products. We make some speculative remarks related to reproducing the above four-point tree level amplitude in the open sector, from a field theory.

scholarly journals HIGGS MECHANISM WITH A TOPOLOGICAL TERM

2001 ◽  
Vol 16 (23) ◽  
pp. 1493-1503 ◽  
Author(s):  
ICHIRO ODA
Keyword(s):  
Degrees Of Freedom ◽  
Goldstone Boson ◽  
Higgs Mechanism ◽  
Tree Level ◽  
Gauge Fields ◽  
Massless Scalar ◽  
Time Dimension ◽  
Superstring Theory ◽  
Gauge Groups ◽  
Topological Term

In cases of both Abelian and non-Abelian gauge groups, we consider the Higgs mechanism in topologically massive gauge theories in an arbitrary space–time dimension. It is shown that the presence of a topological term makes it possible to shift mass of gauge fields in a nontrivial way compared to the conventional value at the classical tree level. We correct the previous misleading statement with respect to the counting of physical degrees of freedom, where it is shown that gauge fields become massive by "eating" the Nambu–Goldstone boson and a higher-rank tensor field, but a new massless scalar appears in the spectrum so the number of physical degrees of freedom remains unchanged before and after the spontaneous symmetry breakdown. Some related phenomenological implications and applications to superstring theory are briefly commented.

scholarly journals The eikonal approach to gravitational scattering and radiation at $$ \mathcal{O} $$(G3)

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Paolo Di Vecchia ◽  
Carlo Heissenberg ◽  
Rodolfo Russo ◽  
Gabriele Veneziano
Keyword(s):  
Classical Limit ◽  
Deflection Angle ◽  
Radiation Reaction ◽  
Tree Level ◽  
Potential Region ◽  
Tree Level Amplitude ◽  
Gravitational Scattering ◽  
Real Emission ◽  
Massless Fields ◽  
Scattering And Radiation

Abstract Using $$ \mathcal{N} $$ N = 8 supergravity as a theoretical laboratory, we extract the 3PM gravitational eikonal for two colliding massive scalars from the classical limit of the corresponding elastic two-loop amplitude. We employ the eikonal phase to obtain the physical deflection angle and to show how its non-relativistic (NR) and ultra-relativistic (UR) regimes are smoothly connected. Such a smooth interpolation rests on keeping contributions to the loop integrals originating from the full soft region, rather than restricting it to its potential sub-region. This task is efficiently carried out by using the method of differential equations with complete near-static boundary conditions. In contrast to the potential-region result, the physical deflection angle includes radiation-reaction contributions that are essential for recovering the finite and universal UR limit implied by general analyticity and crossing arguments. We finally discuss the real emission of massless states, which accounts for the imaginary part of the 3PM eikonal and for the dissipation of energy-momentum. Adopting a direct approach based on unitarity and on the classical limit of the inelastic tree-level amplitude, we are able to treat $$ \mathcal{N} $$ N = 8 and General Relativity on the same footing, and to complete the conservative 3PM eikonal in Einstein’s gravity by the addition of the radiation-reaction contribution. We also show how this approach can be used to compute waveforms, as well as the differential and integrated spectra, for the different radiated massless fields.

scholarly journals FLAVORED CP ASYMMETRIES FOR TYPE II SEESAW LEPTOGENESIS

2013 ◽  
Vol 28 (31) ◽  
pp. 1350165 ◽  
Author(s):  
R. GONZÁLEZ FELIPE ◽  
F. R. JOAQUIM ◽  
H. SERÔDIO
Keyword(s):  
Wave Function ◽  
Lepton Number ◽  
Baryon Asymmetry ◽  
Tree Level ◽  
Type Ii ◽  
Cp Asymmetry ◽  
Lepton Flavor ◽  
Tree Level Amplitude ◽  
The One ◽  
Cp Asymmetries

A novel contribution to the leptonic CP asymmetries in type II seesaw leptogenesis scenarios is obtained for the cases in which flavor effects are relevant for the dynamics of leptogenesis. In the so-called flavored leptogenesis regime, the interference between the tree-level amplitude of the scalar triplet decaying into two leptons and the one-loop wave function correction with leptons in the loop, leads to a new nonvanishing CP asymmetry contribution. The latter conserves total lepton number but violates lepton flavor. Cases in which this novel contribution may be dominant in the generation of the baryon asymmetry are briefly discussed.

scholarly journals Tree-level S-matrix of Pohlmeyer reduced form of AdS 5 × S 5 superstring theory

2010 ◽  
Vol 2010 (2) ◽  
Author(s):  
B. Hoare ◽  
A.A. Tseytlin
Keyword(s):  
Reduced Form ◽  
Tree Level ◽  
Superstring Theory ◽  
S Matrix

RENORMALIZATION EFFECTS IN THE SUPERSTRING MODULI FROM THE HIGHER-DERIVATIVE TERMS

2001 ◽  
Vol 16 (19) ◽  
pp. 3217-3235 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Equation Of State ◽  
Kinetic Energy ◽  
Canonical Form ◽  
Dimensional Reduction ◽  
Scalar Fields ◽  
Adiabatic Index ◽  
Einstein Metric ◽  
Tree Level ◽  
Superstring Theory ◽  
Higher Derivative

The dimensional reduction of the effective ten-action [Formula: see text] of the heterotic superstring theory to the physical four-action S[gij] results in the appearance of three moduli B(a), whose real parts [Formula: see text], set equal for simplicity, define the radius and shape of the compact internal six-space [Formula: see text], in addition to the dilaton [Formula: see text], the ten-interval being [Formula: see text]. These scalar fields are massless at tree level and can be put into canonical form with coefficients [Formula: see text] for the positive kinetic-energy terms, when higher-derivative terms are ignored, as found by Witten, so that [Formula: see text]. Previously, we have shown that σA and σB acquire a potential from the higher-derivative terms [Formula: see text] and [Formula: see text], which becomes large close to the Planck era. Here, we discuss the renormalization of the kinetic-energy terms due to [Formula: see text] which, after diagonalization, results in a mixing of ∇σB with ∇σA, while the remaining coefficient of (∇σB)2 vanishes at t c ≈ t P /12 in a radiation-dominated Universe, corresponding to a temperature T c ≈ 5 × 1017 GeV , where the four-theory is still classical. At earlier times, the energy is unbounded from below, signalling that the four-theory has become unphysical, and that the string must still be in its uncompactified form with one dilaton ϕ, whose canonical kinetic energy is positive in the Einstein metric. This mechanism depends upon the equation of state of the source for the Friedmann expansion assumed, and is only effective for values of the adiabatic index in the range 1.14 < γ < 2.63, which thus includes radiation (γ = 4/3) and the Zel'dovich equation of state (γ = 2).

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