Early work by Bose on the statistics of photons and by Einstein on the condensation of a non-interacting gas of bosons into a single-particle macroscopic ground state has influenced the understanding ...of coherent ground states in super-fluids, superconductors, and laser-cooled atoms. This review focuses on the physics of anti-ferromagnetic phases in quantum magnets and their description with bosonic models. This article reviews experimental and theoretical work on Bose-Einstein condensation in quantum magnets. These magnets are natural realizations of gases of interacting bosons whose relevant parameters such as dimensionality, lattice geometry, amount of disorder, nature of the interactions, and particle concentration can vary widely between different compounds. The plethora of other bosonic phases that can emerge in quantum magnets, of which the Bose-Einstein condensate is the most basic ground state, is reviewed. The possibility of using controlled theoretical approaches has triggered the discovery of unusual effects induced by frustration, dimensionality, or disorder.
As part of efforts to reduce pressure on the Amazon and other biomes, one approach considered by Brazilian authorities and scientists is more intensive use of the soils of the interior of the ...northeast of the country, which are generally sandy, with low contents of organic matter and low water holding capacity and are frequently affected by severe droughts. In this work, biochars produced from waste biomasses were tested for the improvement of these soils. The highest BET (Brunauer-Emmett-Teller) specific surface areas were observed for all biochars. In the pH range studied, the water hyacinth plants (WH) sample showed the most negative zeta potentials, as well as the highest water holding capacity (WHC) values, while the zeta potentials of two quartzarenic neosol soils were consistent with their WHC values. The results suggested that despite the effect of porosity on water retention, the zeta potential could be associated with the presence of negative charges by which hydrated cationic counterions were absorbed and retained. The surface energy and its polar and dispersive components were associated with water retention, with sugar cane bagasse, orange peel, and water hyacinth biochars presenting higher SE values and larger polar components.
We study the Kondo Lattice and the Hubbard models on a triangular lattice. We find that at the mean-field level, these rotationally invariant models naturally support a noncoplanar chiral magnetic ...ordering. It appears as a weak-coupling instability at the band filling factor 3/4 due to the perfect nesting of the itinerant electron Fermi surface. This ordering is a triangular-lattice counterpart of the collinear Neel ordering that occurs on the half-filled square lattice. While the long-range magnetic ordering is destroyed by thermal fluctuations, the chirality can persist up to a finite temperature, causing a spontaneous quantum Hall effect in the absence of any externally applied magnetic field.
It has been reported that vitamin D regulates the immune system. However, whether vitamin D repletion modulates inflammatory responses in lymphocytes from dialysis patients is unclear. In the ...clinical trial, thirty-two (32) dialysis patients with 25 vitamin D ≤ 20ng/mL were randomized to receive either supplementation of cholecalciferol 100,000 UI/week/3 months (16 patients) or placebo (16 patients). In the in vitro study, B and T lymphocytes from 12 healthy volunteers (HV) were incubated with or without uremic serum in the presence or absence of 25 or 1,25 vitamin D. We evaluated the intracellular expression of IL-6, IFN-γ TLR7, TLR9, VDR, CYP27b1 and CYP24a1 by flow cytometry. We observed a reduction in the expression of TLR7, TLR9, INF-γ and CYP24a1 and an increase in VDR and CYP27b1 expression in patients which were supplemented with cholecalciferol, whereas no differences were found in the placebo group. Uremic serum increased the intracellular expression of IL-6, IFN-γ, TLR7, TLR9, VDR, CYP27b1 and CYP24a1. Treatment with 25 or 1,25 vitamin D decreased IL-6 and TLR9. CYP24a1 silencing plus treatment with 25 and/or 1,25 vitamin D had an additional reduction effect on IL-6, IFN-γ, TLR7 and TLR9 expression. This is the first study showing that cholecalciferol repletion has an anti-inflammatory effect and improves vitamin D intracellular regulatory enzymes on lymphocytes from dialysis patients.
Several neurological diseases (e.g. essential tremor and Parkinson’s disease) are related to pathologically enhanced synchronization of bursting neurons. Suppression of these synchronized rhythms has ...potential implications in electrical deep-brain stimulation research. We consider a simplified model of a neuronal network where the local dynamics presents a bursting timescale, and the connection architecture displays the scale-free property (power-law distribution of connectivity). The networks exhibit collective oscillations in the form of synchronized bursting rhythms, without affecting the fast timescale dynamics. We investigate the suppression of these synchronized oscillations using a feedback control in the form of a time-delayed signal. We located domains of bursting synchronization suppression in terms of perturbation strength and time delay, and present computational evidence that synchronization suppression is easier in scale-free networks than in the more commonly studied global (mean-field) networks.
Quantum fluctuations become particularly relevant in highly frustrated quantum magnets and can lead to new states of matter. We provide a simple and robust scenario for inducing magnetic vortex ...crystals in frustrated Mott insulators. By considering a quantum paramagnet that has a gapped spectrum with six-fold degenerate low-energy modes, we study the magnetic-field-induced condensation of these modes. We use a dilute gas approximation to demonstrate that a plethora of multi-Q condensates are stabilized for different combinations of exchange interactions. This rich quantum phase diagram includes magnetic vortex crystals, which are further stabilized by symmetric exchange anisotropies. Because skyrmion and domain-wall crystals have already been predicted and experimentally observed, this novel vortex phase completes the picture of emergent crystals of topologically nontrivial spin configurations.
Observational constraints on Rastall’s cosmology Batista, C. E. M.; Fabris, Júlio C.; Piattella, Oliver F. ...
European physical journal. C, Particles and fields,
05/2013, Letnik:
73, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Rastall’s theory is a modification of General Relativity, based on the non-conservation of the stress-energy tensor. The latter is encoded in a parameter
γ
such that
γ
=1 restores the usual ∇
ν
T
μν
...=0 law. We test Rastall’s theory in cosmology, on a flat Robertson–Walker metric, investigating a two-fluid model and using the type Ia supernovae Constitution dataset. One of the fluids is pressure-less and obeys the usual conservation law, whereas the other is described by an equation of state
p
x
=
w
x
ρ
x
, with
w
x
constant. The Bayesian analysis of the Constitution set does not strictly constrain the parameter
γ
and prefers values of
w
x
close to −1. We then address the evolution of small perturbations and show that they are dramatically unstable if
w
x
≠−1 and
γ
≠1, i.e. General Relativity is the favored configuration. The only alternative is
w
x
=−1, for which the dynamics becomes independent from
γ
.
We review dark energy models that can present non-negligible fluctuations on scales smaller than Hubble radius. Both linear and nonlinear evolutions of dark energy fluctuations are discussed. The ...linear evolution has a well-established framework, based on linear perturbation theory in General Relativity, and is well studied and implemented in numerical codes. We highlight the main results from linear theory to explain how dark energy perturbations become important on the scales of interest for structure formation. Next, we review some attempts to understand the impact of clustering dark energy models in the nonlinear regime, usually based on generalizations of the Spherical Collapse Model. We critically discuss the proposed generalizations of the Spherical Collapse Model that can treat clustering dark energy models and their shortcomings. Proposed implementations of clustering dark energy models in halo mass functions are reviewed. We also discuss some recent numerical simulations capable of treating dark energy fluctuations. Finally, we summarize the observational predictions based on these models.
Chimera states are Spatio-temporal patterns in coupled oscillator arrays, in which incoherent domains coexist with coherent ones. To characterize chimeras, however, is a nontrivial problem since it ...is difficult to distinguish between coherent domains and incoherent domains. A useful tool for this task is machine learning, in particular deep learning techniques like reservoir computing and multilayer perceptrons. In this work we use these quantifiers in order to identify chimera states in logistic map lattices with non-local coupling. We compare our results from machine learning techniques with more conventional characterizations, such as Lyapunov exponents and a local order parameter.
•We use deep learning algorithms to predict state of chimeras in logistically coupled map networks.•We verified which parameters of logistically coupled map networks form chimeras.•We demonstrate that chimeras are always in a transition region between periodic and chaotic dynamics.
Abstract
Electrons at the border of localization generate exotic states of matter across all classes of strongly correlated electron materials and many other quantum materials with emergent ...functionality. Heavy electron metals are a model example, in which magnetic interactions arise from the opposing limits of localized and itinerant electrons. This remarkable duality is intimately related to the emergence of a plethora of novel quantum matter states such as unconventional superconductivity, electronic-nematic states, hidden order and most recently topological states of matter such as topological Kondo insulators and Kondo semimetals and putative chiral superconductors. The outstanding challenge is that the archetypal Kondo lattice model that captures the underlying electronic dichotomy is notoriously difficult to solve for real materials. Here we show, using the prototypical strongly-correlated antiferromagnet CeIn
3
, that a multi-orbital periodic Anderson model embedded with input from ab initio bandstructure calculations can be reduced to a simple Kondo-Heisenberg model, which captures the magnetic interactions quantitatively. We validate this tractable Hamiltonian via high-resolution neutron spectroscopy that reproduces accurately the magnetic soft modes in CeIn
3
, which are believed to mediate unconventional superconductivity. Our study paves the way for a quantitative understanding of metallic quantum states such as unconventional superconductivity.
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