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Effective field theory
About: Effective field theory is a research topic. Over the lifetime, 11711 publications have been published within this topic receiving 343782 citations.
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TL;DR: In this article, the authors study the connection between self-acceleration and the presence of ghosts for a quite generic class of theories that modify gravity in the infrared, defined as those that at distances shorter than cosmological, reduce to a certain generalization of the Dvali-Gabadadze-Porrati (DGP) effective theory.
Abstract: In the Dvali-Gabadadze-Porrati (DGP) model, the "self-accelerating" solution is plagued by a ghost instability, which makes the solution untenable. This fact, as well as all interesting departures from general relativity (GR), are fully captured by a four-dimensional effective Lagrangian, valid at distances smaller than the present Hubble scale. The 4D effective theory involves a relativistic scalar pi, universally coupled to matter and with peculiar derivative self-interactions. In this paper, we study the connection between self-acceleration and the presence of ghosts for a quite generic class of theories that modify gravity in the infrared. These theories are defined as those that at distances shorter than cosmological, reduce to a certain generalization of the DGP 4D effective theory. We argue that for infrared modifications of GR locally due to a universally coupled scalar, our generalization is the only one that allows for a robust implementation of the Vainshtein effect-the decoupling of the scalar from matter in gravitationally bound systems-necessary to recover agreement with solar-system tests. Our generalization involves an internal Galilean invariance, under which pi's gradient shifts by a constant. This symmetry constrains the structure of the pi Lagrangian so much so that in 4D there exist only five terms that can yield sizable nonlinearities without introducing ghosts. We show that for such theories in fact there are "self-accelerating" de Sitter solutions with no ghostlike instabilities. In the presence of compact sources, these solutions can support spherically symmetric, Vainshtein-like nonlinear perturbations that are also stable against small fluctuations. We investigate a possible infrared completion of these theories at scales of order of the Hubble horizon, and larger. There are however some features of our theories that may constitute a problem at the theoretical or phenomenological level: the presence of superluminal excitations; the extreme subluminality of other excitations, which makes the quasistatic approximation for certain solar-system observables unreliable due to Cherenkov emission; the very low strong-interaction scale for pi pi scatterings.
2,086 citations
TL;DR: Four-dimensional covariant nonlinear theories of massive gravity are constructed which are ghost-free in the decoupling limit to all orders, and the Hamiltonian constraint is maintained at least up to and including quartic order in nonlinearities, hence excluding the possibility of the Boulware-Deser ghost up to this order.
Abstract: We construct four-dimensional covariant nonlinear theories of massive gravity which are ghost-free in the decoupling limit to all orders. These theories resum explicitly all the nonlinear terms of an effective field theory of massive gravity. We show that away from the decoupling limit the Hamiltonian constraint is maintained at least up to and including quartic order in nonlinearities, hence excluding the possibility of the Boulware-Deser ghost up to this order. We also show that the same remains true to all orders in a similar toy model.
1,909 citations
Book•
21 Jan 1988
TL;DR: The Landay Theory of Germi Liquids has been used in this paper to describe the second quantization and coherent states of the first quantization of a function at finite temperature.
Abstract: * Second Quantization and Coherent States * General Formalism at Finite Temperature * Perturbation Theory at Zero Temperature * Order Parameters and Broken Symmetry * Greens Functions * The Landay Theory of Germi Liquids * Further Development of Functional Integrals * Stochastic Methods
1,619 citations
TL;DR: In this article, it was shown that supersymmetry breaking necessarily generates at one loop a scalar and gaugino mass as a consequence of the super-Weyl anomaly.
1,586 citations
TL;DR: In this article, a relationship between UV and IR cutoffs is proposed to reconcile the success of local quantum field theory in describing observed particle phenomenology, such that an effective field theory should be a good description of nature.
Abstract: Bekenstein has proposed the bound S{le}{pi}M{sup 2}{sub P}L{sup 2} on the total entropy S in a volume L{sup 3} . This nonextensive scaling suggests that quantum field theory breaks down in large volume. To reconcile this breakdown with the success of local quantum field theory in describing observed particle phenomenology, we propose a relationship between UV and IR cutoffs such that an effective field theory should be a good description of nature. We discuss implications for the cosmological constant problem. We find a limitation on the accuracy which can be achieved by conventional effective field theory. {copyright} {ital 1999} {ital The American Physical Society}
1,371 citations