# Indian physicist questions physical reality of 'Dark Energy'

Bangalore: A research paper by an Indian physicist has for the first time cast doubts on some of the fundamental hypotheses of the standard Big Bang model for the origin of the universe.

Abhas Mitra is working in the Astrophysics Sciences Division of Bhabha Atomic Research Centre (BARC) in Mumbai. His paper that raises several questions for mainstream cosmologists was published earlier this month in the online issue of "Scientific Reports", a new peer-reviewed journal of the prestigious Nature Publishing Group.

The Big Bang model claims that the universe suddenly erupted out of nothingness in an infinitely powerful explosion some 13.7 billion years ago. Mitra's paper raises doubts over physical realization of the key concepts like 'Dark Energy and 'Cosmic Inflation' that are the hallmarks of mainstream cosmology.

In his paper, Mitra argues that that Cosmological Constant, which is the fundamental ingredient behind such concepts like Dark Energy and Cosmic Inflation, should actually be non-existent or zero and cannot have a finite value as believed now.

Modern Big Bang cosmology has in its foundation a feature called "inflation". As per this inflationary Big Bang theory, the universe went through a momentary phase of an exponential expansion almost immediately after its birth. It was hypothesized that the new-born universe developed a positive Cosmological Constant - representing a fairly large repulsive vacuum energy - that gave rise to this runaway expansion. Further, from 1998 onwards, the mainstream cosmology believes that the universe is undergoing an "accelerated" expansion - the extra push coming from a "repulsive" Cosmological Constant that is termed Dark Energy.

Historically, such an exponential expansion is known as a "de-Sitter phase" named after the famous Dutch physicist Williem de-Sitter (1872-1934). But the supposed de-Sitter expansion or inflation has a "very perplexing" aspect, says Mitra.

"While some observers do perceive the explosion, there are other observers who do not at all see the explosion. On the other hand, in physics, and in Einstein's General Relativity, a genuine physical effect must be perceived by all," Mitrra said.

The bottom line of Mitra's highly mathematical paper is that a quantity called "Expansion Scalar" must objectively decide whether there is any genuine expansion or not. "However, the fact that the de-Sitter phase appears at a standstill to some observers means that this is inherently zero, and which in turn implies that Gravitational Constant is actually zero," Mitra said.

Therefore, according to the BARC physicist, the de-Sitter explosion picture obtained by assuming a finite Gravitational Constant is only a "mathematical mirage".

Mitra argues that, accordingly, the Dark Energy and apparent acceleration of the cosmos too could be "fictitious" as these concepts were introduced to explain "a complex inhomogeneous universe in terms of an over-simplified Big Bang model."

Interestingly, he says that the so-called "String Theory", which purports to unify fundamental interactions like electromagnetic and nuclear forces with gravity, also invokes an attractive (instead of repulsive) "anti-de-Sitter" feature that is "basically a profound conjecture".

"I am especially happy that this work has fundamental importance in not only in cosmology but also in physics," Mitra said. His 2009 paper published in the Journal of Mathematical Physics claimed to have proven that the mathematical Black Holes have zero mass, implying that the "Black Hole Candidates" observed by astronomers must be quasi-Black Holes rather than true Black Holes.