7,812 research outputs found
Fermionic entanglement ambiguity in non-inertial frames
We analyse an ambiguity in previous works on entanglement of fermionic fields
in non-inertial frames. This ambiguity, related to the anticommutation
properties of field operators, leads to non-unique results when computing
entanglement measures for the same state. We show that the ambiguity disappears
when we introduce detectors, which are in any case necessary as a means to
probe the field entanglement.Comment: 9 pages, 4 figures. Revtex 4.1, added Journal referenc
An empirical calibration of nebular abundances based on the sulphur emission lines
We present an empirical calibration of nebular abundances based on the strong
emission lines of [SII] and [SIII] in the red part of the spectrum through the
definition of a sulphur abundance parameter S23. This calibration presents two
important advantages against the commonly used one based on the optical oxygen
lines: it remains single-valued up to abundances close to solar and is rather
independent of the degree of ionization of the nebula.Comment: 10 pages, 8 figures. Accepted for publication in MNRA
FINANCIAL INNOVATIONS: SOLUTIONS TO THE EXTERNAL DEBT PROBLEM IN LATIN AMERICA?
Financial Economics,
Relaxion Monodromy and the Weak Gravity Conjecture
The recently proposed relaxion models require extremely large trans-Planckian
axion excursions as well as a potential explicitly violating the axion shift
symmetry. The latter property is however inconsistent with the axion
periodicity, which corresponds to a gauged discrete shift symmetry. A way to
make things consistent is to use monodromy, i.e. both the axion and the
potential parameters transform under the discrete shift symmetry. The structure
is better described in terms of a 3-form field coupling to
the SM Higgs through its field strength . The 4-form also couples linearly
to the relaxion, in the Kaloper-Sorbo fashion. The extremely small
relaxion-Higgs coupling arises in a see-saw fashion as , with
being the axion decay constant. We discuss constraints on this type of
constructions from membrane nucleation and the Weak Gravity Conjecture. The
latter requires the existence of membranes, whose too fast nucleation could in
principle drive the theory out of control, unless the cut-off scale is lowered.
This allows to constrain relaxion models on purely theoretical grounds. We also
discuss possible avenues to embed this structure into string theory.Comment: 26 pages + appendices, 3 figures; v3: Corrected bounds on relaxion
parameter spac
Complex Scalar DM in a B-L Model
In this work, we implement a complex scalar Dark Matter (DM) candidate in a
gauge extension of the Standard Model. The model contains three
right handed neutrinos with different quantum numbers and a rich scalar sector,
with extra doublets and singlets. In principle, these extra scalars can have
VEVs ( and for the extra doublets and singlets,
respectively) belonging to different energy scales. In the context of
, which allows to obtain naturally
light active neutrino masses and mixing compatible with neutrino experiments,
the DM candidate arises by imposing a symmetry on a given complex
singlet, , in order to make it stable. After doing a study of the
scalar potential and the gauge sector, we obtain all the DM dominant processes
concerning the relic abundance and direct detection. Then, for a representative
set of parameters, we found that a complex DM with mass around GeV, for
example, is compatible with the current experimental constraints without
resorting to resonances. However, additional compatible solutions with heavier
masses can be found in vicinities of resonances. Finally, we address the issue
of having a light CP-odd scalar in the model showing that it is safe concerning
the Higgs and the boson invisible decay widths, and also the energy
loss in stars astrophysical constraints.Comment: 20 pages, 3 figure
A 300 GHz "Always-in-Focus" Focusing System for Target Detection
A focusing system for a 300 GHz radar with 5 m target distance and 10 mm diameter spot size resolution is proposed. The focusing system is based on a Gaussian telescope scheme and its main parameters have been de¬signed using Gaussian beam quasi-optical propagation theory with an in-house developed MATLAB® based analysis tool. Then, this approach has been applied to a real focusing system based on two elliptical mirrors in order to reduce the distortion and cross-polar level and a plane mirror to provide scanning capabilities. The over¬all system has been simulated with a full-wave electromag¬netic simulator and its behavior is presented. With this approach, the focusing system always works "in-focus" since the only mirror that is rotated when scanning is the output plane mirror, so the beam is almost not distorted. The design process, although based in the well-known Gaussian beam quasi-optical propagation theory, provides a fast and accurate method and minimizes the overall size of the mirrors. As a consequence, the size of the focusing system is also reduced
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