Search results for "Dimensional reduction"
showing 4 items of 14 documents
No-scale D=5 supergravity from Scherk-Schwarz reduction of D=6 theories
2004
We perform a generalized dimensional reduction of six dimensional supergravity theories to five dimensions. We consider the minimal $(2,0)$ and the maximal $(4,4)$ theories. In each case the reduction allows us to obtain gauged supergravities of no-scale type in dimension five with gauge groups that escape previous classifications. In the minimal case, the geometric data of the reduced theory correspond to particular cases of the D=5 real special geometry. In the maximal case we find a four parameter solution which allows partial breaking of supersymmetry.
Higher-order gravity in higher dimensions: geometrical origins of four-dimensional cosmology?
2017
Determining cosmological field equations represents a still very debated matter and implies a wide discussion around different theoretical proposals. A suitable conceptual scheme could be represented by gravity models that naturally generalize Einstein Theory like higher order gravity theories and higher dimensional ones. Both of these two different approaches allow to define, at the effective level, Einstein field equations equipped with source-like energy momentum tensors of geometrical origin. In this paper, it is discussed the possibility to develop a five dimensional fourth order gravity model whose lower dimensional reduction could provide an interpretation of cosmological four dimens…
Use of helicity methods in evaluating loop integrals: A QCD example
1991
We discuss the use of helicity methods in evaluating loop diagrams by analyzing a specific example: the one-loop contribution to e+e- → qqg in massless QCD. By using covariant helicity representations for the spinor and vector wave functions we obtain the helicity amplitudes directly from the Feynman loop diagrams by covariant contraction. The necessary loop integrations are considerably simplified since one encounters only scalar loop integrals after contraction. We discuss crossing relations that allow one to obtain the corresponding one-loop helicity amplitudes for the crossed processes as e.g. qq → (W, Z, γ∗) + g including the real photon cases. As we treat the spin degrees of freedom i…
Dimensional reduction methods in QCD
1994
We apply the technique of dimensional reduction to massless quantum chromodynamics. It is shown that compared to conventional dimensional regularization methods calculations of radiative corrections at the one-loop level are less involved. We discuss the use of helicity methods within this framework and as an application we evaluate the one-loop corrections to the parity-violating cross sections and to the quark forwardbackward asymmetric polarization in\(e^ + e^ - \to V \to q\bar q(g)\). Finally, we demonstrate that further simplifications occur in the computation of structure functions including the parity-violating structure function in quark- and gluoninitiated electroproduction process…