Negative Mass?

What comes first in mind after hearing a word starting with sense of negativity? A mass with negative sign? Or mass is decreasing by itself? But in the field of physics a physical quantity is never changing identity. Then where this word comes from? More often this word is used by physicist and in their language it is defines as “it is the matter whose mass is of opposite sign to the mass of normal matter, e.g. −1 kg” generally it is produced in the region of negative density pressure obtained by Casimir effect. The earliest references to negative weight are due to the observation that metals gain weight when oxidizing in the study of phlogiston theory in the early 1700s.

“I regard the runaway (or self-accelerating) motion so preposterous that I prefer to rule it out by supposing that inertial mass is all positive or all negative” says William B. Bonnor, he also added that the couple of objects would accelerate without limit (except relativistic one); however, the total mass, momentum and energy of the system would remain 0.The equation of momentum gives a clear vision for possibility of negative mass. This behaviour is completely inconsistent with a common-sense approach and the expected behaviour of 'normal' matter; but is completely mathematically consistent and introduces no violation of conservation of momentum or energy. If the masses are equal in magnitude but opposite in sign, then the momentum of the system remains zero if they both travel together and accelerate together, no matter what their speed.

Since Mass Exists, Can There Be Negative Mass?

In electromagnetism one can derive the energy density of a field from Gauss's law, assuming the curl of the field is 0. Performing the same calculation using Gauss's law for gravity produces a negative energy density for a gravitational field. Many experiments regarding the proof of negative mass is done by scientist. Physicist Peter Engels and a team of colleagues at Washington State University claimed to have observed negative mass behaviour in rubidium atoms. On 10 April 2017 Engels team created negative "effective" mass by reducing the temperature of rubidium atoms to near absolute zero generating a Bose-Einstein condensate. By using a laser-trap, the team were able to reverse the spin of some of the rubidium atoms in this state, and observed that once released from the trap, the atoms expanded and displayed properties of negative mass, in particular accelerating towards a pushing force instead of away from it. This kind of negative effective mass is analogous to the well-known apparent negative effective mass of electrons in the upper part of the dispersion bands in solids. However, neither case is negative mass for the purposes of the stress–energy tensor.

Some recent work with metamaterials suggests that some as-yet-undiscovered composite of superconductors, metamaterials and normal matter could exhibit signs of negative effective mass in much the same way as low temperature alloys melt at below the melting point of their components or some semiconductors have negative differential resistance. In quantum mechanics theory of elementary particles, now part of the Standard Model, already included negative solutions. The Standard Model is a generalization of quantum electrodynamics (QED) and negative mass is already built into the theory For energy eigenstates of the Schrödinger equation, the wavefunction is wavelike wherever the particle's energy is greater than the local potential, and exponential-like (evanescent) wherever it is less. Naively, this would imply kinetic energy is negative in evanescent regions (to cancel the local potential). However, kinetic energy is an operator in quantum mechanics and its expectation value is always positive, summing with the expectation value of the potential energy to yield the energy eigenvalue.

Negative mass swing beats the uncertainty principle

For wavefunctions of particles with zero rest mass (such as photons), this means that any evanescent portions of the wavefunction would be associated with a local negative mass–energy. However, the Schrödinger equation does not apply to massless particles; instead the Klein-Gordon equation is required

Rather than dismissing the idea of negative mass, researchers should try to use it to their advantage. Avenues for further study include looking for dynamical models of matter that would give rise to stable negative-mass configurations and exploring the consequences of negative mass in the inflationary phase of the early universe. A plasma of positive- and negative-mass particles during the inflationary epoch would have an important influence on the propagation of gravitational waves, an effect that might be observable in the cosmic microwave background.

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