What is the cosmological constant?

What is the cosmological constant?

The cosmological constant is presumably an enigmatic form of matter or energy that acts in opposition to gravity and is considered by many physicists to be equivalent to dark energy.

Is vacuum energy constant?

However, the vacuum energy is mathematically infinite without renormalization, which is based on the assumption that we can only measure energy in a relative sense, which is not true if we can observe it indirectly via the cosmological constant.

Why is the cosmological constant wrong?

However, when Einstein applied general relativity to the universe as a whole, his theory predicted an unstable universe that would either expand or contract. This revelation persuaded Einstein to abandon the cosmological constant from his field equations as it was no longer necessary to explain an expanding universe.

Is the cosmological constant zero?

The Cosmological Constant is Probably Zero, and a Proof is Possibly Right.

Is cosmological constant a constant?

In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ), alternatively called Einstein’s cosmological constant, is the constant coefficient of a term Albert Einstein temporarily added to his field equations of general relativity.

Why is cosmological constant Lambda?

Einstein first proposed the cosmological constant (not to be confused with the Hubble Constant) usually symbolized by the greek letter “lambda” (Λ), as a mathematical fix to the theory of general relativity. In its simplest form, general relativity predicted that the universe must either expand or contract.

What is Omega in cosmology?

The cosmic density parameter, Ω, is usually expressed as the ratio of the mean density observed to that of the density in a flat Universe. Given all the range of values for the mean density of the Universe, it is strangely close to the density of a flat Universe.

Does vacuum have dark energy?

One way to envisage the dark energy is that it seems to be linked to the vacuum of space. In other words it is an intrinsic property of the vacuum. So, the larger the volume of space, the more vacuum energy (dark energy) is present and the greater its effects.

Can the cosmological constant be negative?

In other words, a negative-cosmological-constant space can’t be sliced into flat spatial slices (you have assumed that the spatial curvature term k is absent as well: with a negative spatial curvature, you could get solutions). In particular, the AdS space can’t be sliced into flat slices.

What is the cosmological constant of a vacuum?

The cosmological constant turns out to be a measure of the energy density of the vacuum – the state of lowest energy – and although we cannot calculate the vacuum energy with any confidence, this identification allows us to consider the scales of various contributions to the cosmological constant [ 14 , 15 ].

What is the relationship between quantum fluctuations and the cosmological constant?

In general relativity, those quantum fluctuations constitute energy that would add to the cosmological constant. However, this calculated vacuum energy density is many orders of magnitude bigger than the observed cosmological constant.

What does it mean when the cosmological constant is zero?

When Λ is zero, this reduces to the field equation of general relativity usually used in the mid-20th century. When T is zero, the field equation describes empty space (the vacuum). The cosmological constant has the same effect as an intrinsic energy density of the vacuum, ρvac (and an associated pressure).

What is the relationship between vacuum energy density and pressure?

A positive vacuum energy density resulting from a cosmological constant implies a negative pressure, and vice versa. If the energy density is positive, the associated negative pressure will drive an accelerated expansion of the universe, as observed.