Strong interactions between electrons in a solid material can lead to surprising properties. A prime example is the Mott insulator, in which suppression of conductivity occurs as a result of ...interactions rather than a filled Bloch band. Proximity to the Mott insulating phase in fermionic systems is the origin of many intriguing phenomena in condensed matter physics, most notably high-temperature superconductivity. The Hubbard model, which encompasses the essential physics of the Mott insulator, also applies to quantum gases trapped in an optical lattice. It is therefore now possible to access this regime with tools developed in atomic physics. However, an atomic Mott insulator has so far been realized only with a gas of bosons, which lack the rich and peculiar nature of fermions. Here we report the formation of a Mott insulator of a repulsively interacting two-component Fermi gas in an optical lattice. It is identified by three features: a drastic suppression of doubly occupied lattice sites, a strong reduction of the compressibility inferred from the response of double occupancy to an increase in atom number, and the appearance of a gapped mode in the excitation spectrum. Direct control of the interaction strength allows us to compare the Mott insulating regime and the non-interacting regime without changing tunnel-coupling or confinement. Our results pave the way for further studies of the Mott insulator, including spin-ordering and ultimately the question of d-wave superfluidity.
The fractal dimensions df of the shore lines of the Mediterranean, the Aegean, the Black Sea, the Bosphorus Straits (on both the Asian and European sides), the Van Lake, and the lake formed by the ...Atatürk Dam have been calculated. Important distinctions have been found and explained.
•Very clearcut quantitative differences between sea, lake, and dam shorelines are calculated.•The respective fractal dimensions are found.•The obtained differences are clearly related to geological formation.
A novel coordination polymer gel based on zirconium(IV) and 2-thiobarbituric (ZrTBA) was synthesized and explored its potential to remediate As(III) from water. Box-Behnken design with desirability ...function and genetic algorithm yielded the optimized conditions (initial concentration=194 mg L-1, dosage = 42.2 mg, time= 95 min and pH = 4.9) for maximum removal efficiency (99.19 %). The experimental saturation capacity for As(III) was 178.30 mg g-1. The steric parameter n > 1 of the best fitted statistical physics model: monolayer with two energies (R2 = 0.987–0.992) suggested multimolecular mechanism with vertical orientation of As(III) molecules onto the two active sites. XPS and FTIR confirmed the two active sites being zirconium and oxygen. The adsorption energies (E1 = 35.81–37.63 kJ/mol; E2 = 29.50–36.49 kJ/mol) and isosteric heat of adsorption indicated that physical forces governed the As(III) uptake. DFT calculations implied that the weak electrostatic interaction and hydrogen bonding were involved. The best fitted (R2>0.99) fractal like pseudo first order model established energetic heterogeneity. ZrTBA showed excellent removal efficiency in the presence of potential interfering ions and could be used up to 5 cycles of adsorption-desorption with < 8 % loss in the efficiency. ZrTBA removed ≥96.06 % As(III) from real water samples spiked at different levels of As(III).
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•First coordination polymer gel based on zirconium and 2-thiobarbituric acid.•First study to date on Coordination polymer gel removing As(III) from water.•Optimization of variables by RSM with both desirability function and genetic algorithm.•Statistical physics model and XPS were used for mechanistic investigation.•Application to real water samples establishes practical utility.
Atmospheric aerosols are suspended particulate matter of varying composition, size, and mixing state. Challenges remain in understanding the impact of aerosols on the climate, atmosphere, and human ...health. The effect of aerosols depends on their physicochemical properties, such as their hygroscopicity, phase state, and surface tension. These properties are dynamic with respect to the highly variable relative humidity and temperature of the atmosphere. Thus, experimental approaches that permit the measurement of these dynamic properties are required. Such measurements also need to be performed on individual, submicrometer-, and supermicrometer-sized aerosol particles, as individual atmospheric particles from the same source can exhibit great variability in their form and function. In this context, this review focuses on the recent emergence of atomic force microscopy as an experimental tool in physical, analytical, and atmospheric chemistry that enables such measurements. Remaining challenges are noted and suggestions for future studies are offered.
The internal organization of complex networks often has striking consequences on either their response to external perturbations or on their dynamical properties. In addition to small-world and ...scale-free properties, clustering is the most common topological characteristic observed in many real networked systems. In this paper, we report an extensive numerical study on the effects of clustering on the structural properties of complex networks. Strong clustering in heterogeneous networks induces the emergence of a core-periphery organization that has a critical effect on the percolation properties of the networks. We observe a novel double phase transition with an intermediate phase in which only the core of the network is percolated and a final phase in which the periphery percolates regardless of the core. This result implies breaking of the same symmetry at two different values of the control parameter, in stark contrast to the modern theory of continuous phase transitions. Inspired by this core-periphery organization, we introduce a simple model that allows us to analytically prove that such an anomalous phase transition is, in fact, possible.
Hydrodynamic Limit for Interacting Neurons De Masi, A.; Galves, A.; Löcherbach, E. ...
Journal of statistical physics,
02/2015, Letnik:
158, Številka:
4
Journal Article
Recenzirano
Odprti dostop
This paper studies the hydrodynamic limit of a stochastic process describing the time evolution of a system with
N
neurons with mean-field interactions produced both by chemical and by electrical ...synapses. This system can be informally described as follows. Each neuron spikes randomly following a point process with rate depending on its membrane potential. At its spiking time, the membrane potential of the spiking neuron is reset to the value 0 and, simultaneously, the membrane potentials of the other neurons are increased by an amount of potential
1
N
. This mimics the effect of chemical synapses. Additionally, the effect of electrical synapses is represented by a deterministic drift of all the membrane potentials towards the average value of the system. We show that, as the system size
N
diverges, the distribution of membrane potentials becomes deterministic and is described by a limit density which obeys a non linear PDE which is a conservation law of hyperbolic type.
•Development of a new statistical physics model.•Interpretation of ternary adsorption of copper (Cu2+), cadmium (Cd2+) and zinc (Zn2+) on bone char.•Development of new microscopic interpretations of ...adsorption mechanisms.
A new statistical physics model is developed to elucidate the ternary adsorption of some heavy metal ions, i.e. copper (Cu2+), cadmium (Cd2+) and zinc (Zn2+) on bone char. The model is derived by the partition function describing the statistical properties in thermodynamic equilibrium of the investigated adsorption system. Ternary equilibrium adsorption isotherms of these heavy metals on bone char are determined and analyzed at different temperatures (30, 40 and 50 °C). The study of the adsorption capacity shows that the bone char is more effective to remove Cu2+ ions, in both single-compound and ternary systems, while Cd2+ and Zn2+ are adsorbed at lower but similar extent. Moreover, in ternary system, all the adsorption capacities are reduced and Cd2+ and Zn2+ experienced the highest competition effects, as their adsorption capacity significantly decreased with respect to single-compound counterparts. On the other hand, the ternary statistical physics model includes several physicochemical parameters that can attribute microscopic insights to the investigated system. The application of this model indicates that all heavy metal ions are mainly bonded by a horizontal position on bone char. By analyzing and comparing the evolution of the number of ions bonded per adsorbent receptor site (RS), an inhibition effect is observed. The new model is also adopted to characterize the energy of the system, in terms of the interactions between heavy metal ions and adsorbent surface. In particular, both single-compound and ternary adsorption on bone char are endothermic and mainly characterized by physisorption, with a tendency to chemisorption, as confirmed by model outcomes.
Realistic fluid–solid interaction potentials are essential in description of confined fluids especially in the case of geometric heterogeneous surfaces. Correlated random field is considered as a ...model of random surface with high geometric roughness. We provide the general theory of effective coarse-grained fluid–solid potential by proper averaging of the free energy of fluid molecules which interact with the solid media. This procedure is largely based on the theory of random processes. We apply first passage time probability problem and assume the local Markov properties of random surfaces. General expression of effective fluid–solid potential is obtained. In the case of small surface irregularities analytical approximation for effective potential is proposed. Both amorphous materials with large surface roughness and crystalline solids with several types of fcc lattices are considered. It is shown that the wider the lattice spacing in terms of molecular diameter of the fluid, the more obtained potentials differ from classical ones. A comparison with published Monte-Carlo simulations was discussed. The work provides a promising approach to explore how the random geometric heterogeneity affects on thermodynamic properties of the fluids.
During the last few years, statistical physics has received increasing attention as a framework for the analysis of real complex systems; yet, this is less clear in the case of international ...political events, partly due to the complexity in securing relevant quantitative data on them. Here, we analyze a detailed dataset of violent events that took place in Ukraine since January 2021 and analyze their temporal and spatial correlations through entropy and complexity metrics and functional networks. Results depict a complex scenario with events appearing in a non-random fashion but with eastern-most regions functionally disconnected from the remainder of the country-something opposing the widespread "two Ukraines" view. We further draw some lessons and venues for future analyses.
We propose an enlarged framework to study transformations that drive an underdamped Brownian particle in contact with a thermal bath from an equilibrium state to a new one in an arbitrarily short ...time. To this end, we make use of a time and space-dependent potential, that plays a dual role: confine the particle, and manipulate the system. In the special case of an isothermal compression or decompression of a harmonically trapped particle, we derive explicit protocols that perform this quick transformation, following an inverse engineering method. We focus on the properties of these protocols, which crucially depend on two key dimensionless numbers that characterize the relative values of the three timescales of the problem, associated with friction, oscillations in the confinement and duration of the protocol. In particular, we show that our protocols encompass the known overdamped version of this problem and extend it to any friction for decompression and to a large range of frictions for compression.
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