On thermodynamic and quantum fluctuations of cosmological constant

We discuss from the condensed-matter point of view the recent idea that the Poisson fluctuations of cosmological constant about zero could be a source of the observed dark energy [1, 2]. We argue that the thermodynamic fluctuations of $\Lambda$ are much bigger. Since the amplitude of fluctuations is $\propto V^{-1/2}$ where $V$ is the volume of the Universe, the present constraint on the cosmological constant provides the lower limit for $V$, which is much bigger than the volume within the cosmological horizon.