[Paper Review] Physical and Cosmological Implications of a Possible Class of Particles Able to Travel Faster than Light

Luis Gonzalez‐Mestres|ArXiv.org|Oct 24, 1996

Experimental and Theoretical Physics Studies4 references19 citations

TL;DR

The paper proposes a theoretical framework in which particles with critical speeds exceeding light speed (superluminal particles) could exist in vacuum, feeling a Minkowskian-like spacetime with a higher effective speed limit than c, while remaining consistent with Lorentz invariance at low energies. These particles would emit Cherenkov radiation in vacuum if v > c, offering detectable signatures in high-energy cosmic ray experiments and potentially explaining unexplained ultra-high-energy cosmic rays and dark matter.

ABSTRACT

If Lorentz invariance is only an approximate property of equations describing a sector of matter above some critical distance scale, the speed of light c will not necessarily be the only critical speed in vacuum. Superluminal sectors of matter may exist related to new degrees of freedom not yet discovered experimentally. The new particles would not be tachyons: they may feel different minkowskian space-times with critical speeds much higher than c and behave kinematically like ordinary particles apart from the difference in critical speed. We present a discussion of possible physical (theoretical and experimental) and cosmological implications of such a scenario, assuming that the superluminal sectors couple weakly to ordinary matter.

Motivation & Objective

• To explore the theoretical possibility of matter sectors with critical speeds exceeding c, challenging the assumption that c is the only fundamental speed in vacuum.
• To investigate how Lorentz invariance could emerge as an effective symmetry for certain matter sectors even if the underlying spacetime geometry is non-Minkowskian.
• To examine cosmological and astrophysical implications of weakly interacting superluminal particles, including their role in dark matter and ultra-high-energy cosmic rays.
• To propose detectable signatures of superluminal particles in high-energy accelerators and cosmic ray detectors, especially via vacuum Cherenkov radiation and inelastic collisions.
• To address the compatibility of such a scenario with standard tests of relativity and the absence of observed violations at low energies.

Proposed method

• Analyzes solutions of Lorentz-invariant equations (e.g., sine-Gordon solitons) in a Galilean background spacetime, showing how such systems can exhibit relativistic kinematics with an effective speed c_o ≠ c.
• Introduces the concept of multiple critical speeds in vacuum, where superluminal particles have a higher critical speed c_i > c, leading to modified relativistic kinematics.
• Applies the Cherenkov radiation mechanism to vacuum: superluminal particles (v > c_i) emit radiation of particles from a lower-critical-speed sector, including ordinary particles.
• Models high-energy production of superluminal particles in astrophysical sources and their interactions with ordinary matter, including energy transfer in inelastic collisions.
• Considers the propagation of superluminal cosmic rays through the Earth and intergalactic medium, noting minimal attenuation due to weak coupling.
• Evaluates event signatures in large-volume detectors, emphasizing non-ionizing, high-energy deposition and potential origin from particles crossing the Earth.

Experimental results

Research questions

• RQ1 Can matter sectors with critical speeds exceeding c exist without violating Lorentz invariance or contradicting low-energy tests of relativity?
• RQ2 What are the observable signatures of superluminal particles in high-energy accelerators and cosmic ray detectors, particularly via vacuum Cherenkov radiation?
• RQ3 How would the existence of superluminal particles affect the standard Big Bang model, large-scale structure formation, and the cosmic microwave background?
• RQ4 Can superluminal particles explain the observed flux of ultra-high-energy cosmic rays above the GZK cutoff, and what constraints do they place on source locations?
• RQ5 What distinguishes events initiated by superluminal primaries from those of ordinary particles or neutrinos in large-volume detectors?

Key findings

• Superluminal particles with critical speeds c_i > c can exist as solutions of Lorentz-invariant equations in a non-Minkowskian background, such as sine-Gordon solitons in a Galilean spacetime.
• These particles would have rest energies proportional to c_i², implying very large rest masses due to the high critical speed.
• At speeds v > c, superluminal particles would emit Cherenkov radiation in vacuum, including ordinary particles, providing a novel source of high-energy cosmic rays.
• High-energy superluminal cosmic rays could traverse the Earth with minimal attenuation and produce detectable inelastic collisions, transferring nearly all their energy to ordinary secondaries.
• Events initiated by superluminal primaries may lack ionization, start anywhere in a detector, and originate from particles crossing the Earth, distinguishing them from neutrino or ordinary cosmic ray events.
• The GZK cutoff for superluminal primaries may be absent or shifted, offering a potential explanation for unexplained ultra-high-energy cosmic ray events above 100 EeV.