Unique gravitational-wave signatures of systems with negative mass: anti-chirps and dynamic constraints ✦
We investigate the observational viability of negative masses. A unified, empirically testable constraint scheme is proposed using both gravitational charge and dynamical probes. We show that while dipole gravitational radiation requires universality of gravitational charge, binary systems with negative mass inevitably produce anomalous effects: anti-chirps, repulsion, and runaway acceleration. These signatures are absent in current gravitational-wave data (LIGO/Virgo), offering a robust exclusion channel independent of modified gravity assumptions.
Context
For decades, the hypothetical negative mass has stirred the minds of physicists: its introduction could explain dark energy and dark matter (the need for which was indicated by observations by Vera Rubin) without new fields. However, until now there has been no direct observational evidence for its existence. The work by Trivedi and Loeb for the first time offers a clear observational selection criterion based on gravitational-wave astronomy.
Methods
The researchers considered two independent approaches. First, they generalized the constraints from dipole gravitational radiation, which follow from observations of binary pulsars and LIGO/Virgo (see work by Jocelyn Bell Burnell on pulsars and Rainer Weiss on LIGO). It turned out that to satisfy these constraints, the gravitational charge of any object, including one with negative mass, must be strictly universal. Second, they analyzed the dynamics of a binary system within the framework of general relativity of Einstein, without assuming any modifications to gravity. The two-body problem was solved with possible negative inertial mass.
Results
Key result: if one of the masses in a binary system is negative, the reduced mass μ becomes negative, and the evolution of the gravitational-wave frequency is described by an expression with negative ˙f — this is the so-called anti-chirp (decrease in frequency instead of the usual increase). Moreover, when the total mass is negative, the system does not form bound orbits at all and flies apart on a dynamical timescale, while for zero total mass a 'runaway' motion arises, lacking periodicity. Analysis of LIGO-Virgo-KAGRA data shows a complete absence of such signals. For example, a pair with |μ|=10 M⊙ and M=20 M⊙ at an initial separation of 1000 km would produce an anti-chirp lasting about 20 seconds.
Implications
Thus, the hypothesis of astrophysical negative masses is effectively ruled out: it is incompatible both with the universality of gravitational charge and with the actual population of gravitational-wave events. This imposes fundamental constraints on any extensions of the Standard Model that allow particles with negative energy. In a cosmological context, negative masses are also problematic for explaining the accelerated expansion of the Universe.
Future development
In the future, detailed numerical simulations of mergers with negative masses within modified gravity theories could be carried out, as well as searches for residual anti-chirps in archival LIGO data using new algorithms. Of particular interest is testing negative masses in the strong-field regime, for example near event horizons.
Impact
The results directly impact theories of dark matter and dark energy, ruling out a whole class of negative mass models, as well as the understanding of fundamental symmetries in gravity.
Next steps
The next step will be to include the effects of rotation and tidal deformation in analytical estimates for more complete coverage of the parameter space, as well as the development of specialized anti-chirp templates for searches in next-generation LIGO data.
Key open problems
The work is directly connected to the cosmological constant problem and the nature of dark energy — one of the greatest unsolved problems in fundamental physics. If negative masses are ruled out, then the crisis of accelerated expansion of the Universe requires alternative solutions, possibly involving quantum corrections to gravity or modifications of general relativity on cosmological scales.
🎯 The paradoxical behavior of negative mass was first described by Hermann Bondi in 1957: if one body has positive inertial mass and the other negative, the forces still obey Newton's third law, but the negative mass accelerates in the direction opposite to the applied force. As a result, both bodies move with the same acceleration in the same direction — the system 'runs away' from itself!
🎬 The idea of negative mass has inspired science fiction writers: physicist Robert Forward, in his novels and scientific works, considered a 'negative matter drive' capable of accelerating a spaceship to sublight speeds without violating conservation laws.
Key numbers
- Upper limit on the dipole radiation parameter B: ≲ 10⁻⁷
- Required difference in gravitational charges Δα_dip: ≈ 0
- Duration of anti-chirp for a pair with masses 10 M⊙ and 20 M⊙ at a distance of 1000 km: ~20 s