The Effective Action Formalism for Cosmological Perturbations

In the early universe, it is important to take into account the quantum effect of gravity to explain the feature of inflation. In this paper, we consider the M-theory effective action which consists of 11-dimensional supergravity and (Weyl)4 terms. The equations of motion are solved perturbatively, and the solution describes the inflation-like expansion in 4-dimensional spacetime. Equations of motion for tensor perturbations around this background are derived perturbatively. We also check that the equations of motion are obtained from the effective action up to the second order of the perturbations. Finally, we solve the equations of motion for the tensor perturbations perturbatively and obtain analytic expressions for them.

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Effective action on global warming?

Power Engineering Journal ◽

10.1049/pe:19900051 ◽

1990 ◽

Vol 4 (6) ◽

pp. 262

Author(s):

P.R. Wyman

Keyword(s):

Global Warming ◽

Effective Action

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Public-private Partnership and Smart Growth — Principles, Challenges, and Mechanisms for Effective Action

Journal of Business and Economics ◽

10.15341/jbe(2155-7950)/12.06.2015/014 ◽

2015 ◽

Vol 6 (12) ◽

pp. 2128-2136 ◽

Cited By ~ 1

Author(s):

Albena Vutsova ◽

Olga Ignatova

Keyword(s):

Effective Action ◽

Smart Growth ◽

Public Private Partnership ◽

Private Partnership

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Supersymmetric hybrid inflation: Explaining the spectrum of cosmological perturbations through a multiple-stage inflationary model

Conference on 3K cosmology ◽

10.1063/1.59346 ◽

1999 ◽

Author(s):

Mairi Sakellariadou

Keyword(s):

Inflationary Model ◽

Cosmological Perturbations ◽

Hybrid Inflation

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More on complex Sachdev-Ye-Kitaev eternal wormholes

Journal of High Energy Physics ◽

10.1007/jhep03(2021)087 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

Pengfei Zhang

Keyword(s):

Black Hole ◽

Ground State ◽

Effective Action ◽

Chemical Potential ◽

Specific Charge ◽

Zero Temperature ◽

Small Coupling ◽

Chemical Potentials ◽

Quench Dynamics ◽

Two Sides

Abstract In this work, we study a generalization of the coupled Sachdev-Ye-Kitaev (SYK) model with U(1) charge conservations. The model contains two copies of the complex SYK model at different chemical potentials, coupled by a direct hopping term. In the zero-temperature and small coupling limit with small averaged chemical potential, the ground state is an eternal wormhole connecting two sides, with a specific charge Q = 0, which is equivalent to a thermofield double state. We derive the conformal Green’s functions and determine corresponding IR parameters. At higher chemical potential, the system transit into the black hole phase. We further derive the Schwarzian effective action and study its quench dynamics. Finally, we compare numerical results with the analytical predictions.

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New bi-harmonic superspace formulation of 4D, $$ \mathcal{N} $$ = 4 SYM theory

Journal of High Energy Physics ◽

10.1007/jhep04(2021)010 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

I. L. Buchbinder ◽

E. A. Ivanov ◽

V. A. Ivanovskiy

Keyword(s):

Effective Action ◽

Harmonic Superspace ◽

Four Dimensions ◽

Yang Mills ◽

Convenient Tool ◽

Leading Term

Abstract We develop a novel bi-harmonic $$ \mathcal{N} $$ N = 4 superspace formulation of the $$ \mathcal{N} $$ N = 4 supersymmetric Yang-Mills theory (SYM) in four dimensions. In this approach, the $$ \mathcal{N} $$ N = 4 SYM superfield constraints are solved in terms of on-shell $$ \mathcal{N} $$ N = 2 harmonic superfields. Such an approach provides a convenient tool of constructing the manifestly $$ \mathcal{N} $$ N = 4 supersymmetric invariants and further rewriting them in $$ \mathcal{N} $$ N = 2 harmonic superspace. In particular, we present $$ \mathcal{N} $$ N = 4 superfield form of the leading term in the $$ \mathcal{N} $$ N = 4 SYM effective action which was known previously in $$ \mathcal{N} $$ N = 2 superspace formulation.

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The fermionic universal one-loop effective action

Journal of High Energy Physics ◽

10.1007/jhep11(2020)078 ◽

2020 ◽

Vol 2020 (11) ◽

Author(s):

Sebastian A. R. Ellis ◽

Jérémie Quevillon ◽

Pham Ngoc Hoa Vuong ◽

Tevong You ◽

Zhengkang Zhang

Keyword(s):

Path Integral ◽

Effective Action ◽

Covariant Derivative ◽

Heavy Fermion ◽

Axial Vector ◽

Derivative Expansion ◽

Universal Structure ◽

Pseudo Scalar ◽

Matching Techniques ◽

Analytical Expressions

Abstract Recent development of path integral matching techniques based on the covariant derivative expansion has made manifest a universal structure of one-loop effective Lagrangians. The universal terms can be computed once and for all to serve as a reference for one-loop matching calculations and to ease their automation. Here we present the fermionic universal one-loop effective action (UOLEA), resulting from integrating out heavy fermions (Dirac or Majorana) with scalar, pseudo-scalar, vector and axial-vector couplings. We also clarify the relation of the new terms computed here to terms previously computed in the literature and those that remain to complete the UOLEA. Our results can be readily used to efficiently obtain analytical expressions for effective operators arising from heavy fermion loops [13].

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