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The in-out formalism is a systematic and powerful method for finding the effective actions in an electromagnetic field and a curved spacetime provided that the field equation has explicitly known solutions. The effective action becomes…

High Energy Physics - Theory · Physics 2017-04-05 Sang Pyo Kim

We study the one loop effective action for a class of higher spin fields by using a first-quantized description. The latter is obtained by considering spinning particles, characterized by an extended local supersymmetry on the worldline,…

High Energy Physics - Theory · Physics 2015-04-10 Fiorenzo Bastianelli , Roberto Bonezzi , Olindo Corradini , Emanuele Latini

Since the first attempts to quantize Gauge Theories and Gravity in the loop representation, the problem of the determination of the corresponding classical actions has been raised. Here we propose a general procedure to determine these…

High Energy Physics - Theory · Physics 2010-11-01 Daniel Armand-Ugon , Rodolfo Gambini , Jorge Griego , Leonardo Setaro

We study the one-loop contributions of matter and radiation to the gravitational polarization tensor at finite temperatures. Using the analytically continued imaginary-time formalism, the contribution of matter is explicitly given to…

High Energy Physics - Theory · Physics 2009-10-22 A. P. de Almeida , F. T. Brandt , J. Frenkel

The fermionic dispersion relation in the presence of a background magnetic field and a high temperature QED plasma is calculated exactly in the external field, using the Hard Thermal Loop effective action. As the field strength increases…

High Energy Physics - Phenomenology · Physics 2009-10-28 Per Elmfors

A general effective action for quark matter at nonzero temperature and/or nonzero density is derived. Irrelevant quark modes are distinguished from relevant quark modes, and hard from soft gluon modes, by introducing two separate cut-offs…

Nuclear Theory · Physics 2017-08-23 P. T. Reuter , Q. Wang , D. H. Rischke

We derive an effective classical theory for real-time SU($N$) gauge theories at high temperature. By separating off and integrating out quantum fluctuations we obtain a 3D classical path integral over the initial fields and conjugate…

High Energy Physics - Phenomenology · Physics 2009-10-31 B. J. Nauta , Ch. G. van Weert

We compute the effective action for a massive scalar field in (A)dS spacetime using the Euclidean heat kernel method. We highlight that in even-dimensional dS spacetimes, the effective action exhibits a non-trivial imaginary part,…

General Relativity and Quantum Cosmology · Physics 2024-10-29 Yu Zhou , Hai-Qing Zhang

We study the one-loop effective action for a generic two-dimensional dilaton gravity theory conformally coupled to $N$ matter fields. We obtain an explicit expression for the effective action in the weak-coupling limit under a suitable…

High Energy Physics - Theory · Physics 2009-01-16 A. Mikovic , V. Radovanovic

We revise the calculation of the one-loop effective action for scalar and spinor fields coupled to the dilaton in two dimensions. Applying the method of covariant perturbation theory for the heat kernel we derive the effective action in an…

High Energy Physics - Theory · Physics 2016-09-06 Yu. V. Gusev , A. I. Zelnikov

We provide a new and completely general formalism to compute the effective field theory matching contributions from integrating out massive fields in a manifestly gauge covariant way, at any desired loop order. The formalism is based on old…

High Energy Physics - Phenomenology · Physics 2023-04-28 Gero von Gersdorff , Kevin Santos

In this paper we calculate the effective action for neutral particles with anomalous magnetic moment in an external magnetic and electric field. We show that we can take advantage from the Foldy Wouthuysen transformation for such systems,…

High Energy Physics - Theory · Physics 2015-06-05 A. Barducci , R. Giachetti

Dispersion relations for fermions at high temperature and in a background magnetic field are calculated in two different ways. First from a straightforward one-loop calculation where, in the weak field limit, we find an expression closely…

High Energy Physics - Phenomenology · Physics 2007-05-23 Per Elmfors

Integrating out fast varying quantum fluctuations about Yang--Mills fields A_i and A_4, we arrive at the effective action for those fields at high temperatures. Assuming that the fields A_i and A_4 are slowly varying but that the amplitude…

High Energy Physics - Phenomenology · Physics 2014-11-17 D. Diakonov , M. Oswald

Curvature expansion for the heat kernel trace and the one-loop effective action is built for the wave operator of the theory in the quasi-thermal setup of a nonvacuum quantum state. This setup implies a non-static and non-stationary…

High Energy Physics - Theory · Physics 2026-05-13 Andrei O. Barvinsky , Farahmand Hasanov , Nikita Kolganov

Brief review of principal ideas in respect of the high frequency gravitational radiation generated and detected in the laboratory condition is presented. Interaction of electro-magnetic and gravitational waves into a strong magnetic field…

General Relativity and Quantum Cosmology · Physics 2015-04-27 N. I. Kolosnitsyn , V. N. Rudenko

We obtain the effective Lagrangian of static gravitational fields interacting with a QED plasma at high temperature. Using the equivalence between the static hard thermal loops and those with zero external energy-momentum, we compute the…

High Energy Physics - Theory · Physics 2015-06-17 F. T. Brandt , J. Frenkel , J. B. Siqueira

We advance a novel method for the finite-temperature effective action for nonequilibrium quantum fields and find the QED effective action in time-dependent electric fields, where charged pairs evolve out of equilibrium. The imaginary part…

High Energy Physics - Theory · Physics 2014-11-21 Sang Pyo Kim , Hyun Kyu Lee , Yongsung Yoon

We consider a lattice gauge theory at finite temperature in ($d$+1) dimensions with the Wilson action and different couplings $\beta_t$ and $\beta_s$ for timelike and spacelike plaquettes. By using the character expansion and…

High Energy Physics - Lattice · Physics 2009-10-28 M. Billo' , M. Caselle , A. D'Adda , S. Panzeri

The generating functional for hard thermal loops in QCD is important in setting up a resummed perturbation theory. I review how this functional is related to the eikonal for a Chern-Simons theory, and using an auxiliary field, to the gauged…

High Energy Physics - Theory · Physics 2007-05-23 V. P. Nair