22,862 research outputs found
Fluctuations of the Casimir-like force between two membrane inclusions
Although Casimir forces are inseparable from their fluctuations, little is
known about these fluctuations in soft matter systems. We use the membrane
stress tensor to study the fluctuations of the membrane-mediated Casimir-like
force. This method enables us to recover the Casimir force between two
inclusions and to calculate its variance. We show that the Casimir force is
dominated by its fluctuations. Furthermore, when the distance d between the
inclusions is decreased from infinity, the variance of the Casimir force
decreases as -1/d^2. This distance dependence shares a common physical origin
with the Casimir force itself.Comment: 5 pages, 3 figure
The Casimir force of Quantum Spring in the (D+1)-dimensional spacetime
The Casimir effect for a massless scalar field on the helix boundary
condition which is named as quantum spring is studied in our recent
paper\cite{Feng}. In this paper, the Casimir effect of the quantum spring is
investigated in -dimensional spacetime for the massless and massive
scalar fields by using the zeta function techniques. We obtain the exact
results of the Casimir energy and Casimir force for any , which indicate a
symmetry of the two space dimensions. The Casimir energy and Casimir
force have different expressions for odd and even dimensional space in the
massless case but in both cases the force is attractive. In the case of
odd-dimensional space, the Casimir energy density can be expressed by the
Bernoulli numbers, while in the even case it can be expressed by the
-function. And we also show that the Casimir force has a maximum value
which depends on the spacetime dimensions. In particular, for a massive scalar
field, we found that the Casimir force varies as the mass of the field changes.Comment: 9 pages, 5 figures, v2, massive case added, refs. adde
Three dimensional Casimir piston for massive scalar fields
We consider Casimir force acting on a three dimensional rectangular piston
due to a massive scalar field subject to periodic, Dirichlet and Neumann
boundary conditions. Exponential cut-off method is used to derive the Casimir
energy in the interior region and the exterior region separated by the piston.
It is shown that the divergent term of the Casimir force acting on the piston
due to the interior region cancels with that due to the exterior region, thus
render a finite well-defined Casimir force acting on the piston. Explicit
expressions for the total Casimir force acting on the piston is derived, which
show that the Casimir force is always attractive for all the different boundary
conditions considered. As a function of a -- the distance from the piston to
the opposite wall, it is found that the magnitude of the Casimir force behaves
like when and decays exponentially when .
Moreover, the magnitude of the Casimir force is always a decreasing function of
a. On the other hand, passing from massless to massive, we find that the effect
of the mass is insignificant when a is small, but the magnitude of the force is
decreased for large a in the massive case.Comment: 22 pages, 8 figure
Casimir piston for massless scalar fields in three dimensions
We study the Casimir piston for massless scalar fields obeying Dirichlet
boundary conditions in a three dimensional cavity with sides of arbitrary
lengths and where is the plate separation. We obtain an exact
expression for the Casimir force on the piston valid for any values of the
three lengths. As in the electromagnetic case with perfect conductor
conditions, we find that the Casimir force is negative (attractive) regardless
of the values of , and . Though cases exist where the interior
contributes a positive (repulsive) Casimir force, the total Casimir force on
the piston is negative when the exterior contribution is included. We also
obtain an alternative expression for the Casimir force that is useful
computationally when the plate separation is large.Comment: 19 pages,3 figures; references updated and typos fixed to match
published versio
The Casimir Effect in the Presence of Compactified Universal Extra Dimensions
The Casimir force in a system consisting of two parallel conducting plates in
the presence of compactified universal extra dimensions (UXD) is analyzed. The
Casimir force with UXDs differs from the force obtained without extra
dimensions. A new power law for the Casimir force is derived. By comparison to
experimental data the size R of the universal extra dimensions can be
restricted to R < 10 nm for one extra dimension.Comment: 4 pages, 1 figure, error in polarizations corrected, Casimir Effect
in 4D-limit reproduce
Normal and lateral Casimir force: Advances and prospects
We discuss recent experimental and theoretical results on the Casimir force
between real material bodies made of different materials. Special attention is
paid to calculations of the normal Casimir force acting perpendicular to the
surface with the help of the Lifshitz theory taking into account the role of
free charge carriers. Theoretical results for the thermal Casimir force acting
between metallic, dielectric and semiconductor materials are presented and
compared with available experimental data. Main attention is concentrated on
the possibility to control the magnitude and sign of the Casimir force for
applications in nanotechnology. In this respect we consider experiments on the
optical modulation of the Casimir force between metal and semiconductor test
bodies with laser light. Another option is the use of ferromagnetic materials,
specifically, ferromagnetic dielectrics. Under some conditions this allows to
get Casimir repulsion. The lateral Casimir force acting between sinusoidally
corrugated surfaces can be considered as some kind of noncontact friction
caused by zero-point oscillations of the electromagnetic field. Recent
experiments and computations using the exact theory have demonstrated the role
of diffraction-type effects in this phenomenon and the possibility to get
asymmetric force profiles. Conclusion is made that the Casimir force may play
important role in the operation of different devices on the nanoscale.Comment: 27 pages, 13 figures; Invited keynote lecture at the 2nd
International Conference on Science of Friction, Ise-Shima, Mie, Japan,
September 13-18, 2010; to appear in J. Phys.: Conf. Se
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