Experimental estimation of Asymmetry of Radiation for Wheeler-Feynman theory for gravitational waves (2512.20692v1)

Abstract: Wheeler-Feynman absorber theory assumes there should be both retarded EM waves but also advanced, however, with symmetric 1/2-1/2 contributions. In contrast, observed Asymmetry of Radiation like inspiraling has lead to currently default assumption of 1-0 only retarded. Any convex combination is allowed, its choice should depend on the boundary conditions like imbalance between absorbers and emitters - while we have domination of absorbers, it does not need to be complete, suggesting to estimate emitters/absorbers asymmetry parameter from data. It could lead to confirmation of current assumption, or requirement to also include advanced waves into considerations. Experimental estimation of such Asymmetry of Radiation is currently difficult for EM waves due to asymmetry between receivers and transmitters. However, e.g. LIGO just measures lengths, which are invariant to T/CPT symmetry, making available gravitational wave observations appropriate for such estimation. We also discuss other arguments for nonzero contributions of advanced waves. For example gravitational observation of e.g. neutron star merger, with required but clearly missing (retarded) EM counterpart, would leave possibility of being advanced wave. Also there are observed events happening too early according to current knowledge e.g. mergers of black holes in the Mass Gap, or insufficient number of retarded sources e.g. for vibrations of the Universe observed by Pulsar Timing Arrays.

• The paper experimentally estimates the asymmetry parameter (α) in gravitational wave radiation using LIGO data.
• It introduces a framework to detect potential advanced wave contributions through analysis of time-reversed chirp signals.
• Findings may prompt revisions to current models of radiation, altering our understanding of time symmetry in universe dynamics.

Experimental Estimation of Asymmetry of Radiation in Wheeler-Feynman Theory for Gravitational Waves

Introduction and Motivation

The paradigm in modern theoretical physics is founded on the symmetry of dynamical equations under combined CPT transformations, particularly in general relativity and quantum field theory. Nonetheless, phenomena such as the observed irreversibility of radiation—manifested, for instance, in the inspiraling of binary systems emitting gravitational waves—betray an asymmetry in physical solutions, distinguished by their boundary conditions rather than the laws themselves. The Wheeler-Feynman absorber theory, formulated within the context of electromagnetism, postulates that fields should comprise equal parts of retarded and advanced components. However, empirical data in both the electromagnetic and gravitational domains currently favor an overwhelmingly retarded (future-directed) radiation scenario. This work scrutinizes the implicit assumption of perfect asymmetry and proposes an experimental program to estimate the asymmetry parameter from gravitational wave data, particularly leveraging the time-symmetry invariance of LIGO's observable. The outcome could either consolidate prevailing models or motivate the inclusion of advanced wave contributions in gravitational wave astrophysics (2512.20692).

Figure 1: Illustration of symmetric emission of gravitational waves from orbiting masses and the hypothesized contribution of advanced waves; a foundation for asymmetric modeling and experimental testing using LIGO data.

Theoretical Framework: Asymmetry in Radiation

1. Retarded/Advanced Solutions in Electromagnetism and Gravity

The Maxwell and linearized Einstein field equations, being second order in time, admit both retarded and advanced solutions. Classical field theory thus allows for any convex combination of forward and backward-in-time propagating components. The Wheeler-Feynman framework prescribes an equal (1/2, 1/2) weighting, in contrast with conventional models where only retarded fields are physically instantiated. The deviation from perfect symmetry is attributed not to the field equations, but to cosmological boundary conditions—primarily, imbalance between absorbers (future boundary) and emitters (past boundary).

Figure 2: Schematic depiction of boundary-condition-driven asymmetry (parameter $\alpha$) between emitters and absorbers, with implications for the directionality of observable radiation.

Concretely, the asymmetry is parameterized ($c^-$ for retarded, $c^+$ for advanced, with $c^- + c^+ = 1$) as:

$$c^- = \frac{1}{1 + \alpha}, \quad c^+ = \frac{\alpha}{1 + \alpha}$$

where $\alpha \geq 0$ encodes the relative abundance of absorbers versus emitters. This construction generalizes to gravitational fields; the trace-reversed potential in linearized gravity follows a homologous structure in its Green's function decomposition.

2. Measurement Implications: Why Gravitational Waves?

Electromagnetic detectors (antennas, telescopes) are engineered as absorbers, creating intrinsic experimental difficulties for direct advanced-wave detection. In contrast, gravitational wave detectors like LIGO measure geometric strain, inherently invariant under T/CPT transformations, and are thus promising candidates for probing potential advanced contributions in the gravitational sector.

Figure 3: Illustration of the experimental asymmetry in electromagnetic detection and the underlying reason advanced electromagnetic waves have not been observed with conventional instruments.

Experimental Proposals and Phenomenology

Several empirical avenues are outlined for constraining or revealing a nonzero asymmetry parameter ($\alpha$):

• Missing Electromagnetic Counterparts: Neutron star mergers should, under retarded emission dominance, produce detectable EM signatures. Events with absent EM counterparts, beyond plausible detection limits, would strengthen the case for advanced-wave involvement in gravitational radiation.
• Events Beyond the Age of the Universe: Some LIGO-observed events, when interpreted solely as retarded signals, imply source times inconsistent with the cosmic age, especially when accounting for luminosity distance and redshift ambiguities. Advanced-wave admixtures could reconcile these anomalies.
• Black Hole Mergers in the So-Called Mass Gap: Events such as GW190521 present formation scenarios that are highly unlikely under stringent retarded-only assumptions due to insufficient time for necessary hierarchical mergers—but would be more plausible if advanced components are admitted.
• Pulsar Timing Arrays and Universe Vibrations: Observations from MeerKAT and related arrays reveal stochastic gravitational wave backgrounds that seemingly require a supermassive black hole merger rate exceeding what is allowed retardedly. Inclusion of advanced contributions could resolve this tension.

Prospective Experimental Signatures

A particularly distinctive observable would be chirp shapes reversed in time—advanced gravitational waveforms—a scenario especially relevant under a hypothesized cosmic Big Crunch. Empirically, detecting such waveforms would constitute direct evidence of advanced wave contributions and necessitate a profound revision of radiative boundary assumptions.

Figure 4: Hypothetical reversed chirp shapes in gravitational wave data, potentially originating from advanced waves in a contracting (Big Crunch) cosmology.

Implications and Future Directions

Confirmation of a strictly zero value for $\alpha$ would empirically vindicate the exclusive retarded paradigm and reflect a profound cosmological arrow of time. In contrast, detection of a nonzero $\alpha$ would oblige the inclusion of advanced waves in gravitational wave physics and potentially in cosmology, opening entirely new avenues for the study of time symmetry and the deep structure of the Universe.

Near-term priorities include:

• Statistical estimation of $\alpha$ across gravitational wave event populations;
• Systematic searches for time-reversed chirp signals;
• Improved modeling of cosmological boundary conditions influencing absorber-to-emitter ratios;
• Theoretical generalization to include frequency, polarization, and horizon-scale dependencies;
• Extending analogous strategies to electromagnetic contexts, should technological advances enable time-symmetric detector operation.

Conclusion

This work offers a principled challenge to long-held assumptions regarding the asymmetry of radiation, reframing gravitational wave data as a prime testing ground for Wheeler-Feynman-type theories. By operationalizing the asymmetry parameter $\alpha$, it sets a clear agenda for both theoretical and experimental research. The result of such inquiries holds significance not only for gravitation and radiation theory but also for foundational understanding of time, causality, and the arrow of the Universe.