In Focus: The Einstein Rosen bridge and the Einstein Podolsky Rosen paradox, ER and EPR.

Aug 10, 2019 by Vasundhara Mukherjee #Science & Technology

5 years ago, Juan Maldacena and Leonard Susskind explained to the world that the Einstein Rosen bridge between two black holes is created by EPR-like correlations between the microstates of the two black holes.

This, they called the ER=EPR relation, a geometry entanglement relationship. The entangled particles are connected by a Schwarzschild wormhole. In simpler terms, the ER bridge is a special kind of EPR correlation. Their postulation rested upon these two concepts. ER and EPR are related by more than a common publication in 1935, the year Einstein and his collaborators’ work became prominent on the topic. These physicists suggested that if any two particles are connected by entanglement, then they are effectively joined by a wormhole. Conversely, the connection that physicists call a wormhole is equivalent to entanglement. These are two different ways of describing the same reality.

Ron Cowen, published an article in Nature magazine,”The quantum source of space-time”, where he further enhanced on Maldacena and Susskind’s work. The quantum entanglement they talk of is related to a wormhole from general relativity. Susskind has worked on this topic and published a paper in 2016.

The EPR correlations cannot be used to send information faster than the speed of light, Maldacena and Susskind said. In the same vein, Einstein Rosen bridges did not permit us to send a signal from one asymptotic region to the other.

In the year 1935, Einstein explained that the general theory of relativity had an imperfection. As a field theory, it was not complete as it represented the motion of particles by the geodesic equation. Under the influence of a gravitational field, a mass point moves on a geodesic line. With a complete theory, the problem lies in the kinds of aspects it implements. A complete field theory implements only fields and not the concepts of particle and motion. Again, in a complete field theory, they have to exist as a part of it and cannot exist independently on their own. In order to demonstrate that the field equations for empty space are enough to determine the motion of mass points, Einstein worked extensively on it. It is in 1935 that he decided to present a answer that accomplishes a unification of gravitation and electromagnetism. For this purpose, he and Rosen needed a description of a particle without singularity. They joined two Schwarzschild solutions at the Schwarzschild limit and excluded part of the space-time beyond the Schwarzschild singularity. To showcase this in a natural way, they presented the Einstein Rosen bridge solution.

What exactly is the Einstein Rosen bridge solution? In the paper, he nullified the possibility that particles were represented as singularities of the gravitational field because of his polemic with Ludwig Silberstein. Silberstein, a Polish-American physicist toiled in the field of general relativity and special relativity and demonstrated how general relativity was problematic. It is due to his demonstration of the problem that he thought that Einstein’s field equations should be modified together with his general theory of relativity. Einstein remarked, that “matter particles could not be represented as singularities in the field.”

For Rosen and Einstein, the problem of Schwarzschild singularity prompted them to permanently dismiss it and remain fixed on the fundamental principle that singularities of the field are to be excluded. Einstein rationalized that one of the imperfections of the general theory of relativity was that as a field theory it wasn’t complete as it represented the motion of particles by the geodesic equation. His search for complete descriptions of physical conditions in quantum mechanics is also widely known. The two-body problem was a heuristic guide in the hunt for a solution to the problem that the psi function cannot be interpreted as a complete description of a physical condition of one system. It is for this reason that he proposed the EPR paradox along with Rosen and Podolsky.