Defining the Work Done on an Electromagnetic Field.

PAPER pubmed Physical review letters 2018 Other Effect: unclear Evidence: Insufficient

Read original paper → DOI: 10.1103/physrevlett.121.240602 PMID: 30608735 Evidence Lab

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.

AI evidence extraction

At a glance

Study type

Other

Effect direction

unclear

Population

—

Sample size

—

Exposure

Evidence strength

Insufficient

Confidence: 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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    "study_type": "other",
    "exposure": {
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        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
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    },
    "population": null,
    "sample_size": null,
    "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",
    "limitations": [],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "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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