skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Is the effective potential effective for dynamics?
We critically examine the applicability of the effective potential within dynamical situations and find, in short, that the answer is negative. An important caveat of the use of an effective potential in dynamical equations of motion is an explicit violation of energy conservation. An effective potential is introduced in a consistent quasistatic approximation, and its narrow regime of validity is discussed. Two ubiquitous instances in which even the adiabatic effective potential is not valid in dynamics are studied in detail: parametric amplification in the case of oscillating mean fields, and spinodal instabilities associated with spontaneous symmetry breaking. In both cases profuse particle production is directly linked to the failure of the effective potential to describe the dynamics. We introduce a consistent, renormalized, energy conserving dynamical framework that is amenable to numerical implementation. Energy conservation leads to the emergence of asymptotic highly excited, entangled stationary states from the dynamical evolution. As a corollary, decoherence via dephasing of the density matrix in the adiabatic basis is argued to lead to an emergent entropy, formally equivalent to the entanglement entropy. The results suggest novel characterization of asymptotic equilibrium states in terms of order parameter vs energy density. Published by the American Physical Society2024  more » « less
Award ID(s):
2412374
PAR ID:
10596759
Author(s) / Creator(s):
; ;
Corporate Creator(s):
Editor(s):
Tirziu, Alin
Publisher / Repository:
physical review D
Date Published:
Journal Name:
Physical Review D
Edition / Version:
1
Volume:
109
Issue:
10
ISSN:
2470-0010
Page Range / eLocation ID:
1-27
Subject(s) / Keyword(s):
Effective potential, non equilibrium dynamics
Format(s):
Medium: X Size: 27 pages Other: xls
Size(s):
27 pages
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Physical Review D)
    Tirziu, Alin (Ed.)
    We study the applicability of the finite temperature effective potential in the equation of motion of a homogeneous “misaligned” scalar condensate φ and find important caveats that severely restrict its domain of validity: (i) the of local thermodynamic equilibrium is in general not warranted, (ii) we show a direct relation between the effective potential and the thermodynamic entropy density S = − ∂ V eff ( T , φ ) / ∂ T , which entails that for a dynamical φ ( t ) the entropy becomes a nonmonotonic function of time, (iii) parametric instabilities in both cases with and without spontaneous symmetry breaking lead to profuse particle production with nonthermal distribution functions, (iv) in the case of spontaneous symmetry breaking spinodal instabilities yield a complex effective potential, internal energy and , an untenable situation in thermodynamics. All these caveats associated with using the effective potential in the of the condensate cannot be overcome by finite temperature equilibrium resummation schemes. We argue that the dynamics of the condensate leads to decoupling and freeze-out from local thermodynamic equilibrium, and propose a quantum system approach based on unitary time evolution. It yields the correct equations of motion without the caveats of the effective potential, and provides a fully renormalized and thermodynamically consistent framework to study the dynamics of the “misaligned” condensate, with real and conserved energy and entropy amenable to numerical study. The evolution of the condensate leads to profuse with nonthermal distribution functions. Possible emergent asymptotic nonthermal states and eventual rethermalization are conjectured. Published by the American Physical Society2025 
    more » « less
  2. ; ; ; (, Physical Review Letters)
    We introduce an effective field theory (EFT) for conformal impurity by considering a pair of transversely displaced impurities and integrating out modes with mass inversely proportional to the separation distance. This EFT captures the universal signature of the impurity seen by a heavy local operator. We focus on the case of conformal boundaries and derive universal formulas from this EFT for the boundary structure constants at high energy. We point out that the more familiar thermal EFT for conformal field theory is a special case of this EFT with distinguished conformal boundaries. We also derive, for general conformal impurities, nonpositivity and convexitylike constraints on the Casimir energy which determines the leading EFT coefficient. Published by the American Physical Society2024 
    more » « less
  3. ; (, Physical Review Letters)
    The near equality of the dark matter and baryon energy densities is a remarkable coincidence, especially when one realizes that the baryon mass is exponentially sensitive to UV parameters in the form of dimensional transmutation. We explore a new dynamical mechanism, where in the presence of an arbitrary number density of baryons and dark matter, a scalar adjusts the masses of dark matter and baryons until the two energy densities are comparable. In this manner, the coincidence is explained regardless of the microscopic identity of dark matter and how it was produced. This new scalar causes a variety of experimental effects such as a new force and a (dark) matter density-dependent proton mass. Published by the American Physical Society2024 
    more » « less
  4. ; (, Physical Review D)
    Early dark energy solutions to the Hubble tension introduce an additional scalar field which is frozen at early times but becomes dynamical around matter-radiation equality. In order to alleviate the tension, the scalar’s share of the total energy density must rapidly shrink from ∼ 10 % at the onset of matter domination to ≪ 1 % by recombination. This typically requires a steep potential that is imposed rather than emerging from a concrete particle physics model. Here, we point out an alternative possibility: a homogeneous scalar field coupled quadratically to a cosmological background of light thermal relics (such as the Standard Model neutrino) will acquire an effective potential which can reproduce the dynamics necessary to alleviate the tension. We identify the relevant parameter space for this “thermocoupled” scenario and study its unique phenomenology at the background level, including the back-reaction on the neutrino mass. Follow-up numerical work is necessary to determine the constraints placed on the model by early time measurements. Published by the American Physical Society2025 
    more » « less
  5. ; ; (, Physical Review D)
    We elaborate on a recently proposed geometric framework for scalar effective field theories. Starting from the action, a metric can be identified that enables the construction of geometric quantities on the associated functional manifold. These objects transform covariantly under general field redefinitions that relate different operator bases, including those involving derivatives. We present a novel geometric formula for the amplitudes of the theory, where the vertices in Feynman diagrams are replaced by their geometrized counterparts. This makes the on-shell covariance of amplitudes manifest, providing the link between functional geometry and effective field theories. Published by the American Physical Society2025 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email