3,340 research outputs found
On the one-loop correction of "phi^4" theory in higher dimensions
We have considered phi^4 theory in higher dimensions. Using functional
diagrammatic approach, we computed the one-loop correction to effective
potential of the scalar field in five dimensions. It is shown that phi^4 theory
can be regularised in five dimensions. Temperature dependent one-loop
correction and critical temperature T_c are computed and T_c depends on the
fundamental scale M of the theory. A brief discussion of symmetry restoration
is also presented. The nature of phase transitions is examined and is of second
orderComment: 8 pages, 5 figures. To appear in IJMP
Threshold of Singularity Formation in the Semilinear Wave Equation
Solutions of the semilinear wave equation are found numerically in three
spatial dimensions with no assumed symmetry using distributed adaptive mesh
refinement. The threshold of singularity formation is studied for the two cases
in which the exponent of the nonlinear term is either or . Near the
threshold of singularity formation, numerical solutions suggest an approach to
self-similarity for the case and an approach to a scale evolving static
solution for .Comment: 6 pages, 7 figure
Massless interacting particles
We show that classical electrodynamics of massless charged particles and the
Yang--Mills theory of massless quarks do not experience rearranging their
initial degrees of freedom into dressed particles and radiation. Massless
particles do not radiate. We consider a version of the direct interparticle
action theory for these systems following the general strategy of Wheeler and
Feynman.Comment: LaTeX; 20 pages; V4: discussion is slightly modified to clarify some
important points, relevant references are adde
Dark matter: A spin one half fermion field with mass dimension one?
We report an unexpected theoretical discovery of a spin one half matter field
with mass dimension one. It is based on a complete set of eigenspinors of the
charge conjugation operator. Due to its unusual properties with respect to
charge conjugation and parity it belongs to a non standard Wigner class.
Consequently, the theory exhibits non-locality with (CPT)^2 = - I. Its dominant
interaction with known forms of matter is via Higgs, and with gravity. This
aspect leads us to contemplate it as a first-principle candidate for dark
matter.Comment: 5 pages, RevTex, v2: slightly extended discussion, new refs. and note
adde
Casimir force in the presence of a magnetodielectric medium
In this article we investigate the Casimir effect in the presence of a medium
by quantizing the Electromagnetic (EM) field in the presence of a
magnetodielectric medium by using the path integral formalism. For a given
medium with definite electric and magnetic susceptibilities, explicit
expressions for the Casimir force are obtained which are in agree with the
original Casimir force between two conducting parallel plates immersed in the
quantum electromagnetic vacuum.Comment: 8 pages, 1 figur
Treating some solid state problems with the Dirac equation
The ambiguity involved in the definition of effective-mass Hamiltonians for
nonrelativistic models is resolved using the Dirac equation. The multistep
approximation is extended for relativistic cases allowing the treatment of
arbitrary potential and effective-mass profiles without ordering problems. On
the other hand, if the Schrodinger equation is supposed to be used, our
relativistic approach demonstrate that both results are coincidents if the
BenDaniel and Duke prescription for the kinetic-energy operator is implemented.
Applications for semiconductor heterostructures are discussed.Comment: 06 pages, 5 figure
Cosmological model with non-minimally coupled fermionic field
A model for the Universe is proposed whose constituents are: (a) a dark
energy field modeled by a fermionic field non-minimally coupled with the
gravitational field, (b) a matter field which consists of pressureless baryonic
and dark matter fields and (c) a field which represents the radiation and the
neutrinos. The coupled system of Dirac's equations and Einstein field equations
is solved numerically by considering a spatially flat homogeneous and isotropic
Universe. It is shown that the proposed model can reproduce the expected
red-shift behaviors of the deceleration parameter, of the density parameters of
each constituent and of the luminosity distance. Furthermore, for small values
of the red-shift the constant which couples the fermionic and gravitational
fields has a remarkable influence on the density and deceleration parameters.Comment: Accepted for publication in Europhysics Letter
A Chiral Schwinger model, its Constraint Structure and Applications to its Quantization
The Jackiw-Rajaraman version of the chiral Schwinger model is studied as a
function of the renormalization parameter. The constraints are obtained and
they are used to carry out canonical quantization of the model by means of
Dirac brackets. By introducing an additional scalar field, it is shown that the
model can be made gauge invariant. The gauge invariant model is quantized by
establishing a pair of gauge fixing constraints in order that the method of
Dirac can be used.Comment: 18 page
Covariant Hamiltonian Field Theory
A consistent, local coordinate formulation of covariant Hamiltonian field
theory is presented. Whereas the covariant canonical field equations are
equivalent to the Euler-Lagrange field equations, the covariant canonical
transformation theory offers more general means for defining mappings that
preserve the form of the field equations than the usual Lagrangian description.
It is proved that Poisson brackets, Lagrange brackets, and canonical 2-forms
exist that are invariant under canonical transformations of the fields. The
technique to derive transformation rules for the fields from generating
functions is demonstrated by means of various examples. In particular, it is
shown that the infinitesimal canonical transformation furnishes the most
general form of Noether's theorem. We furthermore specify the generating
function of an infinitesimal space-time step that conforms to the field
equations.Comment: 93 pages, no figure
Relativistic entanglement of two massive particles
We describe the spin and momentum degrees of freedom of a system of two
massive spin-- particles as a 4 qubit system. Then we explicitly
show how the entanglement changes between different partitions of the qubits,
when considered by different inertial observers. Although the two particle
entanglement corresponding to a partition into Alice's and Bob's subsystems is,
as often stated in the literature, invariant under Lorentz boosts, the
entanglement with respect to other partitions of the Hilbert space on the other
hand, is not. It certainly does depend on the chosen inertial frame and on the
initial state considered. The change of entanglement arises, because a Lorentz
boost on the momenta of the particles causes a Wigner rotation of the spin,
which in certain cases entangles the spin- with the momentum states. We
systematically investigate the situation for different classes of initial spin
states and different partitions of the 4 qubit space.
Furthermore, we study the behavior of Bell inequalities for different
observers and demonstrate how the maximally possible degree of violation, using
the Pauli-Lubanski spin observable, can be recovered by any inertial observer.Comment: 17 pages, 4 figure
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