504 research outputs found
Proposed Spontaneous Generation of Magnetic Fields by Curved Layers of a Chiral Superconductor
We demonstrate that two-dimensional chiral superconductors on curved surfaces
spontaneously develop magnetic flux. This geometric Meissner effect provides an
unequivocal signature of chiral super- conductivity, which could be observed in
layered materials under stress. We also employ the effect to explain some
puzzling questions related to the location of zero-energy Majorana modes
Genesis of the Floquet Hofstadter butterfly
We investigate theoretically the spectrum of a graphene-like sample
(honeycomb lattice) subjected to a perpendicular magnetic field and irradiated
by circularly polarized light. This system is studied using the Floquet
formalism, and the resulting Hofstadter spectrum is analyzed for different
regimes of the driving frequency. For lower frequencies, resonances of various
copies of the spectrum lead to intricate formations of topological gaps. In the
Landau-level regime, new wing-like gaps emerge upon reducing the driving
frequency, thus revealing the possibility of dynamically tuning the formation
of the Hofstadter butterfly. In this regime, an effective model may be
analytically derived, which allows us to retrace the energy levels that exhibit
avoided crossings and ultimately lead to gap structures with a wing-like shape.
At high frequencies, we find that gaps open for various fluxes at , and
upon increasing the amplitude of the driving, gaps also close and reopen at
other energies. The topological invariants of these gaps are calculated and the
resulting spectrum is elucidated. We suggest opportunities for experimental
realization and discuss similarities with Landau-level structures in non-driven
systems.Comment: 8 pages, 4 figure
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
Lost in Translation--Multilingual Misinformation and its Evolution
Misinformation and disinformation are growing threats in the digital age, spreading rapidly across languages and borders. This paper investigates the prevalence and dynamics of multilingual misinformation through an analysis of over 250,000 unique fact-checks spanning 95 languages. First, we find that while the majority of misinformation claims are only fact-checked once, 11.7%, corresponding to more than 21,000 claims, are checked multiple times. Using fact-checks as a proxy for the spread of misinformation, we find 33% of repeated claims cross linguistic boundaries, suggesting that some misinformation permeates language barriers. However, spreading patterns exhibit strong homophily, with misinformation more likely to spread within the same language. To study the evolution of claims over time and mutations across languages, we represent fact-checks with multilingual sentence embeddings and cluster semantically similar claims. We analyze the connected components and shortest paths connecting different versions of a claim finding that claims gradually drift over time and undergo greater alteration when traversing languages. Overall, this novel investigation of multilingual misinformation provides key insights. It quantifies redundant fact-checking efforts, establishes that some claims diffuse across languages, measures linguistic homophily, and models the temporal and cross-lingual evolution of claims. The findings advocate for expanded information sharing between fact-checkers globally while underscoring the importance of localized verification
Lost in Translation -- Multilingual Misinformation and its Evolution
Misinformation and disinformation are growing threats in the digital age,
spreading rapidly across languages and borders. This paper investigates the
prevalence and dynamics of multilingual misinformation through an analysis of
over 250,000 unique fact-checks spanning 95 languages. First, we find that
while the majority of misinformation claims are only fact-checked once, 11.7%,
corresponding to more than 21,000 claims, are checked multiple times. Using
fact-checks as a proxy for the spread of misinformation, we find 33% of
repeated claims cross linguistic boundaries, suggesting that some
misinformation permeates language barriers. However, spreading patterns exhibit
strong homophily, with misinformation more likely to spread within the same
language. To study the evolution of claims over time and mutations across
languages, we represent fact-checks with multilingual sentence embeddings and
cluster semantically similar claims. We analyze the connected components and
shortest paths connecting different versions of a claim finding that claims
gradually drift over time and undergo greater alteration when traversing
languages. Overall, this novel investigation of multilingual misinformation
provides key insights. It quantifies redundant fact-checking efforts,
establishes that some claims diffuse across languages, measures linguistic
homophily, and models the temporal and cross-lingual evolution of claims. The
findings advocate for expanded information sharing between fact-checkers
globally while underscoring the importance of localized verification
Description of nuclear systems within the relativistic Hartree-Fock method with zero range self-interactions of the scalar field
An exact method is suggested to treat the nonlinear self-interactions (NLSI)
in the relativistic Hartree-Fock (RHF) approach for nuclear systems. We
consider here the NLSI constructed from the relativistic scalar nucleon
densities and including products of six and eight fermion fields. This type of
NLSI corresponds to the zero range limit of the standard cubic and quartic
self-interactions of the scalar field. The method to treat the NLSI uses the
Fierz transformation, which enables one to express the exchange (Fock)
components in terms of the direct (Hartree) ones. The method is applied to
nuclear matter and finite nuclei. It is shown that, in the RHF formalism, the
NLSI, which are explicitly isovector-independent, generate scalar, vector and
tensor nucleon self-energies strongly density-dependent. This strong isovector
structure of the self-energies is due to the exchange terms of the RHF method.
Calculations are carried out with a parametrization containing five free
parameters. The model allows a description of both types of systems compatible
with experimental data.Comment: 23 pages, 14 figures (v2: major quantitative changes
Updated comparison of age estimates from paired calcified structures from Atlantic bluefin tuna
In this paper we present an updated comparison of age estimates from otoliths and spines
from the same specimen, with the intention to analyze whether it is possible to use both
structures in obtaining age-length keys for this species. The agreement between otolith and
spine age estimates was good for bluefin tuna younger than 14 years old with less than one
year difference. Tests of symmetry showed the asymmetrical distribution of ages. However
no significant differences were found between the growth parameters estimated from both
paired hard parts. It is suggested using both structures readings for constructing agelength
keys for bluefin tuna younger than 14 years.En prensa0,000
Overexpression of Mouse D-Type Cyclins Accelerates G(1) Phase in Rodent Fibroblasts
Mammalian D-type cyclins are growth factor-regulated, delayed early response genes that are presumed to control progression through the G1 phase of the cell cycle by governing the activity of cyclin-dependent kinases (cdks). Overexpression of mouse cyclin D1 in serum-stimulated mouse NIH-3T3 and rat-2 fibroblasts increased their rates of G0 to S- and G1- to S-phase transit by several hours, leading to an equivalent contraction of their mean cell generation times. Although such cells remained contact inhibited and anchorage dependent, they manifested a reduced serum requirement for growth and were smaller in size than their normal counterparts. Ectopic expression of cyclin D2 in rodent fibroblasts, either alone or together with exogenous cdk4, shortened their G0- to S-phase interval and reduced their serum dependency, but cyclin D2 alone did not alter cell size significantly. When cells were microinjected during the G2 interval with a monoclonal antibody specifically reactive to cyclin D1, parental rodent fibroblasts and derivatives overexpressing this cyclin were inhibited from entering S phase, but cells injected near the G1/S phase transition were refractory to antibody-induced growth suppression. Thus, cyclin D1, and most likely D2, are rate limiting for G1progression
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