Our universe may have a time-reversed entangled twin 🪞

A new theory suggests our universe and a time-reversed twin could emerge together. This quantum approach avoids singularities and offers an explanation for dark energy.

Traditional cosmological models often rely on the idea of an initial singularity, a point of infinite density. A study recently accepted in Europhysics Letters proposes an alternative: a flat universe and its anti-universe could be born simultaneously through a quantum process. This theory bypasses several problems of previous models like those of Hartle-Hawking and Vilenkin.


The model introduces a 'Euclidean instanton', a phase where time behaves like a spatial dimension. During this phase, the size of the universe follows a cosine-like curve, thus avoiding infinite densities. This approach allows for a smooth transition to the universe we know, with a finite scale factor from the very beginning.

A quantum potential plays a key role by replacing traditional spatial curvature. This idea solves a major problem of earlier theories, which struggled to explain the observed absence of curvature.

CPT symmetry, fundamental in physics, ensures that each universe has a time-reversed twin. These two entities, though classically separate, remain quantumly entangled. This entanglement could shed light on poorly understood cosmological phenomena like dark energy and dark matter.

The implications of this model are vast. It avoids initial singularities, reproduces inflation compatible with observations, and could explain the accelerating expansion of the universe. Moreover, it offers a new avenue for understanding dark matter, linking these mysteries to the very birth of the cosmos.

Future research will need to identify observable signatures of this model, such as specific patterns in the cosmic microwave background. These studies could also bridge quantum mechanics and general relativity, two pillars of physics still poorly reconciled.

What is a Euclidean instanton?

A Euclidean instanton is a solution to physics equations in a space where time behaves like a spatial dimension. This concept is crucial for avoiding singularities in cosmological models.

The instanton enables a smooth transition between a timeless state and our expanding universe. It describes a phase where the size of the universe varies regularly, without reaching infinite density.

This approach is inspired by quantum mechanics, where particles can take classically forbidden paths. The Euclidean instanton thus represents a quantum 'tunnel' between two cosmological states.

Its use in this model avoids the problems posed by singularities while remaining compatible with current observations.

How does CPT symmetry influence cosmology?

CPT symmetry is a fundamental principle in physics, combining charge conjugation, parity inversion, and time reversal. It implies that every physical process has a mirror equivalent.

In the proposed model, this symmetry ensures the simultaneous creation of a universe and its anti-universe. These two entities evolve in opposite time directions but remain quantumly linked.

This entanglement could explain phenomena like dark energy. The anti-universe would act as a source of repulsive energy, accelerating the expansion of our universe.

CPT symmetry thus provides a natural framework for exploring cosmological oddities.