266 research outputs found
Whether an enormously large energy density of the quantum vacuum is catastrophic
The problem of an enormously large energy density of the quantum vacuum is
discussed in connection with the concept of renormalization of physical
parameters in quantum field theory. Using the method of dimensional
regularization, it is recalled that the normal ordering procedure of creation
and annihilation operators is equivalent to a renormalization of the
cosmological constant leading to its zero and nonzero values in Minkowski
space-time and in the standard cosmological model, respectively. It is argued
that a frequently discussed gravitational effect, resulting from an enormously
large energy density described by the nonrenormalized (bare) cosmological
constant, might be nonobservable much like some other bare quantities
introduced in the formalism of quantum field theory.Comment: 6 page
The Nernst heat theorem for an atom interacting with graphene: Dirac model with nonzero energy gap and chemical potential
We derive the low-temperature behavior of the Casimir-Polder free energy for
a polarizable atom interacting with graphene sheet which possesses the nonzero
energy gap and chemical potential . The response of graphene to
the electromagnetic field is described by means of the polarization tensor in
the framework of Dirac model on the basis of first principles of thermal
quantum field theory in the Matsubara formulation. It is shown that the thermal
correction to the Casimir-Polder energy consists of three contributions. The
first of them is determined by the Matsubara summation using the polarization
tensor defined at zero temperature, whereas the second and third contributions
are caused by an explicit temperature dependence of the polarization tensor and
originate from the zero-frequency Matsubara term and the sum of all Matsubara
terms with nonzero frequencies, respectively. The asymptotic behavior for each
of the three contributions at low temperature is found analytically for any
value of the energy gap and chemical potential. According to our results, the
Nernst heat theorem for the Casimir-Polder free energy and entropy is satisfied
for both and . We also reveal an entropic
anomaly arising in the case . The obtained results are discussed
in connection with the long-standing fundamental problem in Casimir physics
regarding the proper description of the dielectric response of matter to the
electromagnetic field.Comment: 37 pages, 1 Table; several typos are correcte
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