1,727 research outputs found

### Comments on branon dressing and the Standard Model

This technical note shows how Electrodynamics and a Yukawa model are dressed
after integrating out perturbative brane fluctuations, and it is found that
first order corrections in the inverse of the brane tension occur for the
fermion and scalar wave functions, the couplings and the masses. Nevertheless,
field redefinitions actually lead to effective actions where only masses are
dressed to this first order. We compare our results with the literature and
find discrepancies at the next order, which, however, might not be measurable
in the valid regime of low-energy brane fluctuations.Comment: 12 page

### Perturbative quantization of two-dimensional space-time noncommutative QED

Using the method of perturbative quantization in the first order
approximation, we quantize a non-local QED-like theory including fermions and
bosons whose interactions are described by terms containing higher order
space-time derivatives. As an example, the two-dimensional space-time
noncommutative QED (NC-QED) is quantized perturbatively up to O(e^2,\theta^3),
where e is the NC-QED coupling constant and \theta is the noncommutativity
parameter. The resulting modified Lagrangian density is shown to include terms
consisting of first order time-derivative and higher order space-derivatives of
the modified field variables that satisfy the ordinary equal-time commutation
relations up to O(e^2,\theta^3. Using these commutation relations, the
canonical current algebra of the modified theory is also derived.Comment: 22 pages, no figure

### First-order quantum correction to the Larmor radiation from a moving charge in a spatially homogeneous time-dependent electric field

First-order quantum correction to the Larmor radiation is investigated on the
basis of the scalar QED on a homogeneous background of time-dependent electric
field, which is a generalization of a recent work by Higuchi and Walker so as
to be extended for an accelerated charged particle in a relativistic motion. We
obtain a simple approximate formula for the quantum correction in the limit of
the relativistic motion when the direction of the particle motion is parallel
to that of the electric field.Comment: 12 pages, 2 figures, accepted for publication in Physical Review

### Vacuum fluctuations in a supersymmetric model in FRW spacetime

We study a noninteracting supersymmetric model in an expanding FRW spacetime.
A soft supersymmetry breaking induces a nonzero contribution to the vacuum
energy density. A short distance cutoff of the order of Planck length provides
a scale for the vacuum energy density comparable with the observed cosmological
constant. Assuming the presence of a dark energy substance in addition to the
vacuum fluctuations of the field an effective equation of state is derived in a
selfconsistent approach. The effective equation of state is sensitive to the
choice of the cut-off but no fine tuning is needed.Comment: 19 pages, accepted for publication in Phys. Rev.

### Dark Matter from R^2-gravity

The modification of Einstein gravity at high energies is mandatory from a
quantum approach. In this work, we point out that this modification will
necessarily introduce new degrees of freedom. We analyze the possibility that
these new gravitational states can provide the main contribution to the
non-baryonic dark matter of the Universe. Unfortunately, the right ultraviolet
completion of gravity is still unresolved. For this reason, we will illustrate
this idea with the simplest high energy modification of the Einstein-Hilbert
action: R^2-gravity.Comment: 5 pages, 2 figure

### Quantum Dynamics for de Sitter Radiation

We revisit the Hamiltonian formalism for a massive scalar field and study the
particle production in a de Sitter space. In the invariant-operator picture the
time-dependent annihilation and creation operators are constructed in terms of
a complex solution to the classical equation of motion for the field and the
Gaussian wave function for each Fourier mode is found which is an exact
solution to the Schr\"odinger equation. The in-out formalism is reformulated by
the annihilation and creation operators and the Gaussian wave functions. The de
Sitter radiation from the in-out formalism differs from the Gibbons-Hawking
radiation in the planar coordinates, and we discuss the discrepancy of the
particle production by the two methodComment: LaTex 12 pages, no figure; CosPA2011, Peking Univ., Oct. 28-31, 2011;
references added; to be published in International Journal of Modern Physics:
Conference Serie

### The Transition Amplitude for 2T Physics

We present the transition amplitude for a particle moving in a space with two
times and D space dimensions having a Sp(2,R) local symmetry and an SO(D,2)
rigid symmetry. It was obtained from the BRST-BFV quantization with a unique
gauge choice. We show that by constraining the initial and final points of this
amplitude to lie on some hypersurface of the D+2 space the resulting amplitude
reproduces well known systems in lower dimensions. This provides an alternative
physical interpretation for two times physics which is derived in a single
framework.Comment: 4 pages, typos corrected, references adde

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