7,636 research outputs found
Attractive and Repulsive Casimir Vacuum Energy with General Boundary Conditions
The infrared behavior of quantum field theories confined in bounded domains
is strongly dependent on the shape and structure of space boundaries. The most
significant physical effect arises in the behaviour of the vacuum energy. The
Casimir energy can be attractive or repulsive depending on the nature of the
boundary. We calculate the vacuum energy for a massless scalar field confined
between two homogeneous parallel plates with the most general type of boundary
conditions depending on four parameters. The analysis provides a powerful
method to identify which boundary conditions generate attractive or repulsive
Casimir forces between the plates. In the interface between both regimes we
find a very interesting family of boundary conditions which do not induce any
type of Casimir force. We also show that the attractive regime holds far beyond
identical boundary conditions for the two plates required by the Kenneth-Klich
theorem and that the strongest attractive Casimir force appears for periodic
boundary conditions whereas the strongest repulsive Casimir force corresponds
to anti-periodic boundary conditions. Most of the analysed boundary conditions
are new and some of them can be physically implemented with metamaterials.Comment: 21 pages, 11 figure
generalized Robin boundary conditions and quantum vacuum fluctuations
The effects induced by the quantum vacuum fluctuations of one massless real
scalar field on a configuration of two partially transparent plates are
investigated. The physical properties of the infinitely thin plates are
simulated by means of Dirac- point interactions. It is
shown that the distortion caused on the fluctuations by this external
background gives rise to a generalization of Robin boundary conditions. The
-operator for potentials concentrated on points with non defined parity is
computed with total generality. The quantum vacuum interaction energy between
the two plates is computed using the formula to find positive, negative,
and zero Casimir energies. The parity properties of the
potential allow repulsive quantum vacuum force between identical plates.Comment: 21 pages and 11 figures. PhysRev
Casimir Effect and Global Theory of Boundary Conditions
The consistency of quantum field theories defined on domains with external
borders imposes very restrictive constraints on the type of boundary conditions
that the fields can satisfy. We analyse the global geometrical and topological
properties of the space of all possible boundary conditions for scalar quantum
field theories. The variation of the Casimir energy under the change of
boundary conditions reveals the existence of singularities generically
associated to boundary conditions which either involve topology changes of the
underlying physical space or edge states with unbounded below classical energy.
The effect can be understood in terms of a new type of Maslov index associated
to the non-trivial topology of the space of boundary conditions. We also
analyze the global aspects of the renormalization group flow, T-duality and the
conformal invariance of the corresponding fixed points.Comment: 11 page
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