19,250 research outputs found
DGSAT: Dwarf Galaxy Survey with Amateur Telescopes II. A catalogue of isolated nearby edge-on disk galaxies and the discovery of new low surface brightness systems
The connection between the bulge mass or bulge luminosity in disk galaxies
and the number, spatial and phase space distribution of associated dwarf
galaxies is a discriminator between cosmological simulations related to galaxy
formation in cold dark matter and generalized gravity models. Here, a nearby
sample of isolated Milky Way class edge-on galaxies is introduced, to
facilitate observational campaigns to detect the associated families of dwarf
galaxies at low surface brightness. Three galaxy pairs with at least one of the
targets being edge-on are also introduced. About 60% of the catalogued isolated
galaxies contain bulges of different size, while the remaining objects appear
to be bulge-less. Deep images of NGC 3669 (small bulge, with NGC 3625 at the
edge of the image) and NGC 7814 (prominent bulge), obtained with a 0.4-m
aperture, are also presented, resulting in the discovery of two new dwarf
galaxy candidates, NGC3669-DGSAT-3 and NGC7814-DGSAT-7. Eleven additional low
surface brightness galaxies are identified, previously notified with low
quality measurement flags in the Sloan Digital Sky Survey (SDSS). Integrated
magnitudes, surface brightnesses, effective radii, Sersic indices, axis ratios,
and projected distances to their putative major hosts are displayed. At least
one of the galaxies, NGC3625-DGSAT-4, belongs with a surface brightness of
approximately 26 mag per arcsec^2 and effective radius >1.5 kpc to the class of
ultra-diffuse galaxies (UDGs). NGC3669-DGSAT-3, the galaxy with lowest surface
brightness in our sample, may also be an UDG.Comment: 12 pages including 6 figures, 4 tables, a brief appendix, accepted
for publication in Astronomy & Astrophysics (A&A). Paper slightly modified
after A&A language editing, updating very few references and correcting a
small typo at the start of the Appendi
Quantum control on entangled bipartite qubits
Ising interaction between qubits could produce distortion in entangled pairs
generated for engineering purposes (as in quantum computation) in presence of
parasite magnetic fields, destroying or altering the expected behavior of
process in which is projected to be used. Quantum control could be used to
correct that situation in several ways. Sometimes the user should be make some
measurement upon the system to decide which is the best control scheme; other
posibility is try to reconstruct the system using similar procedures without
perturbate it. In the complete pictures both schemes are present. We will work
first with pure systems studying advantages of different procedures. After, we
will extend these operations when time of distortion is uncertain, generating a
mixed state, which needs to be corrected by suposing the most probably time of
distortion.Comment: 10 pages, 5 figure
Numerical semigroups problem list
We propose a list of open problems in numerical semigroups.Comment: To appear in the CIM Bulletin, number 33. (http://www.cim.pt/) 13
page
Staircase to Higher-Order Topological Phase Transitions
We find a series of topological phase transitions of increasing order, beyond
the more standard second-order phase transition in a one-dimensional
topological superconductor. The jumps in the order of the transitions depend on
the range of the pairing interaction, which is parametrized by an algebraic
decay with exponent . Remarkably, in the limit the order
of the topological transition becomes infinite. We compute the critical
exponents for the series of higher-order transitions in exact form and find
that they fulfill the hyperscaling relation. We also study the critical
behaviour at the boundary of the system and discuss potential experimental
platforms of magnetic atoms in superconductors.Comment: 5+5pages, 7 figures. Accepted as a Rapid Communicatio
Raman-scattering study of the phonon dispersion in twisted bi-layer graphene
Bi-layer graphene with a twist angle \theta\ between the layers generates a
superlattice structure known as Moir\'{e} pattern. This superlattice provides a
\theta-dependent q wavevector that activates phonons in the interior of the
Brillouin zone. Here we show that this superlattice-induced Raman scattering
can be used to probe the phonon dispersion in twisted bi-layer graphene (tBLG).
The effect reported here is different from the broadly studied double-resonance
in graphene-related materials in many aspects, and despite the absence of
stacking order in tBLG, layer breathing vibrations (namely ZO' phonons) are
observed.Comment: 18 pages, 4 figures, research articl
Warped Fermions and Precision Tests
We analyze the behavior of Standard Model matter propagating in a slice of
AdS_5 in the presence of infrared-brane kinetic terms. Brane kinetic terms are
naturally generated through radiative corrections and can also be present at
tree level. The effect of the brane kinetic terms is to expell the heavy KK
modes from the infrared-brane, and hence to reduce their coupling to the
localized Higgs field. In a previous work we showed that sizable gauge kinetic
terms can allow KK mode masses as low as a few TeV, compatible with present
precision measurements. We study here the effect of fermion brane kinetic terms
and show that they ameliorate the behavior of the theory for third generation
fermions localized away from the infrared brane, reduce the contribution of the
third generation quarks to the oblique correction parameters and mantain a good
fit to the precision electroweak data for values of the KK masses of the order
of the weak scale.Comment: 25 pages, 4 figures, latex2
From stellar to planetary composition: Galactic chemical evolution of Mg/Si mineralogical ratio
The main goal of this work is to study element ratios that are important for
the formation of planets of different masses. We study potential correlations
between the existence of planetary companions and the relative elemental
abundances of their host stars. We use a large sample of FGK-type dwarf stars
for which precise Mg, Si, and Fe abundances have been derived using HARPS
high-resolution and high-quality data. A first analysis of the data suggests
that low-mass planet host stars show higher [Mg/Si] ratios, while giant planet
hosts present [Mg/Si] that is lower than field stars. However, we found that
the [Mg/Si] ratio significantly depends on metallicity through Galactic
chemical evolution. After removing the Galactic evolution trend only the
difference in the [Mg/Si] elemental ratio between low-mass planet hosts and
non-hosts was present in a significant way. These results suggests that
low-mass planets are more prevalent around stars with high [Mg/Si]. Our results
demonstrate the importance of Galactic chemical evolution and indicate that it
may play an important role in the planetary internal structure and composition.Comment: Accepted by A&A (Letter to the Editor
Unifying parameter estimation and the Deutsch-Jozsa algorithm for continuous variables
We reveal a close relationship between quantum metrology and the Deutsch-Jozsa algorithm on continuous-variable quantum systems. We develop a general procedure, characterized by two parameters, that unifies parameter estimation and the Deutsch-Jozsa algorithm. Depending on which parameter we keep constant, the procedure implements either the parameter-estimation protocol or the Deutsch-Jozsa algorithm. The parameter-estimation part of the procedure attains the Heisenberg limit and is therefore optimal. Due to the use of approximate normalizable continuous-variable eigenstates, the Deutsch-Jozsa algorithm is probabilistic. The procedure estimates a value of an unknown parameter and solves the Deutsch-Jozsa problem without the use of any entanglement
Quantum simulation of Anderson and Kondo lattices with superconducting qubits
We introduce a mapping between a variety of superconducting circuits and a
family of Hamiltonians describing localized magnetic impurities interacting
with conduction bands. This includes the Anderson model, the single impurity
one- and two-channel Kondo problem, as well as the 1D Kondo lattice. We compare
the requirements for performing quantum simulations using the proposed circuits
to those of universal quantum computation with superconducting qubits, singling
out the specific challenges that will have to be addressed.Comment: Longer versio
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