Defining the Work Done on an Electromagnetic Field.

Physical review letters · 2018 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 5505

Study snapshot

PublicationPhysical review letters · 2018

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

The problem of defining work done on an electromagnetic field (EMF) via moving charges does not have a ready solution, because the standard Hamiltonian of an EMF-whose time derivative should define the work according to the first law-is not gauge invariant. This limits applications of statistical mechanics to an EMF. We obtained a new, explicitly gauge-invariant Hamiltonian for an EMF that depends only on physical observables. This Hamiltonian allows us to define work and to formulate the second law for an EMF. It also leads to a direct link between this law and the electrodynamic arrow of time, i.e., choosing retarded, and not advanced solutions of wave equations. Measuring the thermodynamic work can determine whether the photon mass is small but nonzero.

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AI evidence extraction

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Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

The authors derive an explicitly gauge-invariant Hamiltonian for an electromagnetic field that depends only on physical observables. Using this Hamiltonian, they define work and formulate the second law for an electromagnetic field, linking it to the electrodynamic arrow of time; they also suggest that measuring thermodynamic work could help determine whether photon mass is small but nonzero.

Outcomes measured

Gauge-invariant Hamiltonian for an electromagnetic field
Definition of thermodynamic work done on an electromagnetic field
Formulation of the second law for an electromagnetic field
Link between second law and electrodynamic arrow of time (retarded vs advanced solutions)
Potential to use thermodynamic work measurements to test whether photon mass is nonzero

View raw extracted JSON

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  "outcomes": [
    "Gauge-invariant Hamiltonian for an electromagnetic field",
    "Definition of thermodynamic work done on an electromagnetic field",
    "Formulation of the second law for an electromagnetic field",
    "Link between second law and electrodynamic arrow of time (retarded vs advanced solutions)",
    "Potential to use thermodynamic work measurements to test whether photon mass is nonzero"
  ],
  "main_findings": "The authors derive an explicitly gauge-invariant Hamiltonian for an electromagnetic field that depends only on physical observables. Using this Hamiltonian, they define work and formulate the second law for an electromagnetic field, linking it to the electrodynamic arrow of time; they also suggest that measuring thermodynamic work could help determine whether photon mass is small but nonzero.",
  "effect_direction": "unclear",
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  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "electromagnetic field",
    "work",
    "Hamiltonian",
    "gauge invariance",
    "statistical mechanics",
    "second law",
    "arrow of time",
    "retarded solutions",
    "advanced solutions",
    "photon mass"
  ],
  "suggested_hubs": []
}

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Identifiers and source

DOI: 10.1103/physrevlett.121.240602
PubMed: 30608735

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