اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدCorrections to the running of gauge couplings due to quantum gravity
109
0
0.0
(
0
)
تأليف
Michael Maziashvili
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Concerning the gravitational corrections to the running of gauge couplings two different results were reported. Some authors claim that gravitational correction at the one-loop level indicates an interesting effect of universal gravitational decreasing of gauge couplings, that is, gravitational correction works universally in the direction of asymptotic freedom no matter how the gauge coupling behaves without gravity, while others reject the presence of gravitational correction at the one-loop level at all. Being these calculations done in the framework of an effective field theory approach to general relativity, we wanted to draw attention to a recently discovered profound quantum-gravitational effect of space-time dimension running that inevitably affects the running of gauge couplings. The running of space-time dimension indicating gradual reduction of dimension as one gets into smaller scales acts on the coupling constants in the direction of asymptotic freedom and therefore in any case manifests the plausibility of this quantum-gravitational effect. Curiously enough, the results are also in perfect quantitative agreement with those of Robinson and Wilczek.
قيم البحث
اقرأ أيضاً
We give a direct microscopic derivation of the F-theory background that corresponds to four D7 branes of type I theory by taking into account the D-instanton contributions to the emission of the axio-dilaton field in the directions transverse to the
D7s. The couplings of the axio-dilaton to the D-instanton moduli modify its classical source terms which are shown to be proportional to the elements of the D7 brane chiral ring. Solving the bulk field equations with the non-perturbatively corrected sources yields the full F-theory background. This solution represents the gravitational dual of the four-dimensional theory living on a probe D3 brane of type I, namely of the N=2, Sp(1) SYM theory with Nf=4. Our results provide an explicit microscopic derivation of the non-perturbative gravitational dual of this theory. They also explain the recent observation that the exact coupling for this theory can be entirely reconstructed from its perturbative part plus the knowledge of the chiral ring on the D7 branes supporting its flavor degrees of freedom.
We discuss a string model where a conformal four-dimensional N=2 gauge theory receives corrections to its gauge kinetic functions from stringy instantons. These contributions are explicitly evaluated by exploiting the localization properties of the i
ntegral over the stringy instanton moduli space. The model we consider corresponds to a setup with D7/D3-branes in type I theory compactified on T4/Z2 x T2, and possesses a perturbatively computable heterotic dual. In the heteoric side the corrections to the quadratic gauge couplings are provided by a 1-loop threshold computation and, under the duality map, match precisely the first few stringy instanton effects in the type I setup. This agreement represents a very non-trivial test of our approach to the exotic instanton calculus.
We discuss a variation of quadratic gravity in which the gravitational interaction remains weakly coupled at all energies, but is assisted by a Yang-Mills gauge theory which becomes strong at the Planck scale. The Yang-Mills interaction is used to in
duce the usual Einstein-Hilbert term, which was taken to be small or absent in the original action. We study the spin-two propagator in detail, with a focus on the high mass resonance which is shifted off the real axis by the coupling to real decay channels. We calculate scattering in the $J=2$ partial wave and show explicitly that unitarity is satisfied. The theory will in general have a large cosmological constant and we study possible solutions to this, including a unimodular version of the theory. Overall, the theory satisfies our present tests for being a ultraviolet completion of quantum gravity.
We study quantum corrections to hypersurfaces of dimension $d+1>2$ embedded in generic higher-dimensional spacetimes. Manifest covariance is maintained throughout the analysis and our methods are valid for arbitrary co-dimension and arbitrary bulk me
tric. A variety of theories which are prominent in the modern amplitude literature arise as special limits: the scalar sector of Dirac-Born-Infeld theories and their multi-field variants, as well as generic non-linear sigma models and extensions thereof. Our explicit one-loop results unite the leading corrections of all such models under a single umbrella. In contrast to naive computations which generate effective actions that appear to violate the non-linear symmetries of their classical counterparts, our efficient methods maintain manifest covariance at all stages and make the symmetry properties of the quantum action clear. We provide an explicit comparison between our compact construction and other approaches and demonstrate the ultimate physical equivalence between the superficially different results.
The quantum contributions to the gravitational action are relatively easy to calculate in the higher derivative sector of the theory. However, the applications to the post-inflationary cosmology and astrophysics require the corrections to the Einstei
n-Hilbert action and to the cosmological constant, and those we can not derive yet in a consistent and safe way. At the same time, if we assume that these quantum terms are covariant and that they have relevant magnitude, their functional form can be defined up to a single free parameter, which can be defined on the phenomenological basis. It turns out that the quantum correction may lead, in principle, to surprisingly strong and interesting effects in astrophysics and cosmology.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
