Attractive Regime Research Articles

TASEP of interacting particles of arbitrary size

A mean-field description of the stationary state behaviour of interacting k-mers performing totally asymmetric exclusion processes (TASEP) on an open lattice segment is presented employing the discrete Takahashi formalism. It is shown how the maximal current and the phase diagram, including triple-points, depend on the strength of repulsive and attractive interactions. We compare the mean-field results with Monte Carlo simulation of three types interacting k-mers: monomers, dimers and trimers. (a) We find that the Takahashi estimates of the maximal current agree quantitatively with those of the Monte Carlo simulation in the absence of interaction as well as in both the the attractive and the strongly repulsive regimes. However, theory and Monte Carlo results disagree in the range of weak repulsion, where the Takahashi estimates of the maximal current show a monotonic behaviour, whereas the Monte Carlo data show a peaking behaviour. It is argued that the peaking of the maximal current is due to a correlated motion of the particles. In the limit of very strong repulsion the theory predicts a universal behavior: th maximal currents of k-mers correspond to that of non-interacting -mers; (b) Monte Carlo estimates of the triple-points for monomers, dimers and trimers show an interesting general behaviour : (i) the phase boundaries and for entry and exit current, respectively, as function of interaction strengths show maxima for whereas exhibit minima at the same strength; (ii) in the attractive regime, however, the trend is reversed (). The Takahashi estimates of the triple-point for monomers show a similar trend as the Monte Carlo data except for the peaking of ; for dimers and trimers, however, the Takahashi estimates show an opposite trend as compared to the Monte Carlo data.

Spreading of correlations in a quenched repulsive and attractive one-dimensional integrable system

We study the real time evolution of the correlation functions in a globally quenched interacting one dimensional lattice system by means of time adaptive density matrix renormalization group. We find a clear light-cone behavior quenching the repulsive interaction from the gapped density wave regime. The spreading velocity increases with the final values of the interaction and then saturates at a certain finite value. In the case of a Luttinger liquid phase as the initial state, for strong repulsive interaction quenches, a more complex dynamics occurs as a result of bound state formations. From the other side in the attractive regime, depending on where connected correlation functions are measured, one can observe a delay in the starting time evolution and a coexistence of ballistic and localized signals.

Conformal quantum mechanics and holography in noncommutative space–time

We analyze the effects of noncommutativity in conformal quantum mechanics (CQM) using the κ-deformed space–time as a prototype. Up to the first order in the deformation parameter, the symmetry structure of the CQM algebra is preserved but the coupling in a canonical model of the CQM gets deformed. We show that the boundary conditions that ensure a unitary time evolution in the noncommutative CQM can break the scale invariance, leading to a quantum mechanical scaling anomaly. We calculate the scaling dimensions of the two and three point functions in the noncommutative CQM which are shown to be deformed. The AdS2/CFT1 duality for the CQM suggests that the corresponding correlation functions in the holographic duals are modified. In addition, the Breitenlohner–Freedman bound also picks up a noncommutative correction. The strongly attractive regime of a canonical model of the CQM exhibit quantum instability. We show that the noncommutativity softens this singular behaviour and its implications for the corresponding holographic duals are discussed.

Discharge Analysis of EAST H-Mode for Designing Compressed Plasma

Some electric parameters of Experimental Advanced Superconducting Tokamak shot #41195 are analyzed out for compressed plasma at its flat-top phase—the phase has 32-s stationary H-mode plasma discharge and the pulse is long enough for accommodating the compression process. A good knowledge of the total plasma inductance is benefit to map the discharging evolution of vertical magnetic field judged by Maxwell equations, whose nonlinear component is to analyze the effect of noninductive current drive, including the effect of bootstrap current. Furthermore, the relationship of vertical magnetic field and line-averaged density is derived and validated during flat-top phase for given plasma current. An increase in magnetic strength of vertical field will allow high temperature, high density, high beta, and high bootstrap current fraction to be achieved, offering an attractive regime for compressed plasma to approach the Lawson parameter.

Quantum state atomic force microscopy

New classical modalities of atomic force microscopy continue to emerge to achieve higher spatial, spectral, and temporal resolution for nanometrology of materials. Here, we introduce the concept of a quantum mechanical modality that capitalizes on squeezed states of probe displacement. We show that such squeezing is enabled nanomechanically when the probe enters the van der Waals regime of interaction with a sample. The effect is studied in the non-contact mode, where we consider the parameter domains characterizing the attractive regime of the probe-sample interaction force.

Phaseless quantum Monte-Carlo approach to strongly correlated superconductors with stochastic Hartree–Fock–Bogoliubov wavefunctions

The so-called phaseless quantum Monte-Carlo method currently offers one of the best performing theoretical framework to investigate interacting Fermi systems. It allows to extract an approximate ground-state wavefunction by averaging independent-particle states undergoing a Brownian motion in imaginary-time. Here, we extend the approach to a random walk in the space of Hartree–Fock–Bogoliubov (HFB) vacua that are better suited for superconducting or superfluid systems. Well-controlled statistical errors are ensured by constraining stochastic paths with the help of a trial wavefunction. It also guides the dynamics and takes the form of a linear combination of HFB ansätze. Estimates for the observables are reconstructed through an extension of Wick’s theorem to matrix elements between HFB product states. The usual combinatory complexity associated to the application of this theorem for four- and more- body operators is bypassed with a compact expression in terms of Pfaffians. The limiting case of a stochastic motion within Slater determinants but guided with HFB trial wavefunctions is also considered. Finally, exploratory results for the spin-polarized Hubbard model in the attractive regime are presented.

Fiscal regime design elements and relative regime ranking for concessions

AbstractThe technological breakthrough in the oil and gas sector has made it possible for the companies to diversify their investment portfolio but it is quite challenging to select a balanced and stable regime to mitigate the country risks associated with investments especially in a volatile price environment. The project economics calculation to evaluate fiscal regime sometimes proves out to be a difficult task for corporate planners to model and make conclusions for investments. It is also a challenge for the government to maximize the revenue from their resources and for the contractor to choose a suitable investment destination. There is a scope in current fiscal analysis literature for a single indicator which can contribute towards the overall comparison of fiscal regimes. This paper will evaluate the design aspects of fiscal terms of a concession regime and will address the generic concern of fiscal regime evaluation through a Relative Fiscal Ranking (The Relative Fiscal Ranking is the evaluation of two or more fiscal regimes benchmarked against the most attractive fiscal regime with desired fiscal terms set/calculated by the investors.) methodology applied on a set of concession regimes. This method will directly establish a unique functionality between the fiscal terms and their attractiveness which will ultimately expose the relative risk associated with fiscal regimes when they are compared against each other. It generates key insights for investment decisions and can help the policy makers and corporate planners to take informed decisions.

Enhanced phase and amplitude image contrasts of polymers in bimodal atomic force microscopy

Higher second free amplitudes beyond the commonly used values show remarkable phase and amplitude contrasts.

Delocalization effects, entanglement entropy and spectral collapse of boson mixtures in a double well

We investigate the ground-state properties of a two-species condensate of interacting bosons in a double-well potential. Each atomic species is described by a two-space-mode Bose–Hubbard model. The coupling of the two species is controlled by the interspecies interaction W. To analyze the ground state when W is varied in both the repulsive () and the attractive () regime, we apply two different approaches. First we solve the problem numerically (i) to obtain an exact description of the ground-state structure and (ii) to characterize its correlation properties by studying (the appropriate extensions to the present case of) the quantum Fisher information, the coherence visibility and the entanglement entropy as functions of W. Then we approach analytically the description of the low-energy scenario by means of the Bogoliubov scheme. In this framework the ground-state transition from delocalized to localized species (with space separation for , and mixing for ) is well reproduced. These predictions are qualitatively corroborated by our numerical results. We show that such a transition features a spectral collapse reflecting the dramatic change of the dynamical algebra of the four-mode model Hamiltonian.

Matrix-product ansatz for the totally asymmetric simple exclusion process with a generalized update on a ring.

We apply the matrix-product ansatz to study the totally asymmetric simple exclusion process on a ring with a generalized discrete-time dynamics depending on two hopping probabilities, p and p[over ̃]. The model contains as special cases the TASEP with parallel update, when p[over ̃]=0, and with sequential backward-ordered update, when p[over ̃]=p. We construct a quadratic algebra and its two-dimensional matrix-product representation to obtain exact finite-size expressions for the partition function, the current of particles, and the two-point correlation function. Our main new result is the derivation of the finite-size pair correlation function. Its behavior is analyzed in different regimes of effective attraction and repulsion between the particles, depending on whether p[over ̃]>p or p[over ̃]<p. In particular, we explicitly obtain an analytic expression for the pair correlation function in the limit of irreversible aggregation p[over ̃]→1, when the stationary configurations contain just one cluster.

On the interaction of dipolar filaments.

The interactions of dipolar filaments such as magnetic needles and chains in strong homogeneous magnetic/electric field are investigated theoretically. Revisiting the case of uniformly magnetized/polarized parallel needles of finite size L and separated by a distance R , all the relevant regimes of attraction and/or repulsion are properly addressed and discussed. At short inter-needle separation ( R/L ≲ 0.2, the repuive pair potential of two facing needles is governed by R(-1) in strong contrast with R(-3) at long separations (R/L ≳ 2.5). This softening is attributed to an efficient long-range screening owing to the relatively long needle extension in this regime. This whole understanding of dipolar needles effective interaction is then used to grasp that of dipolar chains made up of spherical dipolar beads. When excluded-volume correlations are weak (i.e., the chains are a few beads apart), chains and needles possess virtually the same effective interaction. However, at short separation there is a remarkable hardening upon approaching two chains in registry in qualitative contrast to the needles case.

Light-induced optomechanical forces in graphene waveguides

We show that the electromagnetic forces generated by the excitations of a mode in graphene-based optomechanical systems are highly tunable by varying the graphene chemical potential, and orders of magnitude stronger than usual non-graphene-based devices, in both attractive and repulsive regimes. We analyze coupled waveguides made of two parallel graphene sheets, either suspended or supported by dielectric slabs, and study the interplay between the light-induced force and the Casimir-Lifshitz interaction. These findings pave the way to advanced possibilities of control and fast modulation for optomechanical devices and sensors at the nano- and micro-scales.

Superconducting circuit simulator of Bose-Hubbard model with a flat band

Recent advance in quantum simulations of interacting photons using superconducting circuits offers opportunities for investigating the Bose-Hubbard model in various geometries with hopping coefficients and self-interactions tuned to both signs. Here we investigate phenomena related to localized states associated with a flat-band supported by the saw-tooth geometry. A localization-delocalization transition emerges in the non-interacting regime as the sign of hopping coefficient is changed. In the presence of interactions, patterns of localized states approach a uniform density distribution for repulsive interactions while interesting localized density patterns can arise in strongly attractive regime. The density patterns indicate the underlying inhomogeneity of the simulator. Two-particle correlations can further distinguish the nature of the localized states in attractive and repulsive interaction regimes. We also survey possible experimental implementations of the simulator.

Reconstruction of height of sub-nanometer steps with bimodal atomic force microscopy

Obtaining topographic images of surfaces presenting terraces with heights in the nanometer and sub-nanometer range has become routine since the advent of atomic force microscopy (AFM). There remain however several open questions regarding the validity of direct topographic measurements. Here we turn to recent advances in AFM to correct the height of nanometric terraces by exploiting the four observables of bimodal AFM operated in the non-invasive attractive regime. We first derive expressions based on the van der Waals theory and then image model terraces in air in standard bimodal AFM while simultaneously correcting and decoupling the sources of loss/gain of height.

Robust high-resolution imaging and quantitative force measurement with tuned-oscillator atomic force microscopy

Atomic force microscopy (AFM) and spectroscopy are based on locally detecting the interactions between a surface and a sharp probe tip. For highest resolution imaging, noncontact modes that avoid tip–sample contact are used; control of the tip’s vertical position is accomplished by oscillating the tip and detecting perturbations induced by its interaction with the surface potential. Due to this potential’s nonlinear nature, however, achieving reliable control of the tip–sample distance is challenging, so much so that despite its power vacuum-based noncontact AFM has remained a niche technique. Here we introduce a new pathway to distance control that prevents instabilities by externally tuning the oscillator’s response characteristics. A major advantage of this operational scheme is that it delivers robust position control in both the attractive and repulsive regimes with only one feedback loop, thereby providing an easy-to-implement route to atomic resolution imaging and quantitative tip–sample interaction force measurement.

Inflation targeting in developing countries revisited

In a recent paper, Gonçalvez and Salles (2008) (G–S) report that developing countries adopting the inflation targeting (IT) regime experienced greater drops in inflation and GDP growth volatility than non-inflation targeting developing countries. In this paper, I find that the G–S results do not hold up when their analytical framework is employed in the context of a more rational and larger sample of developing countries that controls for the comparability of monetary regimes as suggested by Ball (2010). In particular, adoption of an IT regime did not help reduce inflation and growth volatility in developing countries compared to the average experience with other monetary regimes and was no more advantageous in these regards than the adoption of a hard or crawling peg exchange rate regime. As such, the less technically demanding monetary regime of currency pegging remains an attractive regime option for policymakers in developing countries.

Exact formulas for the form factors of local operators in the Lieb–Liniger model

We present exact formulas for the form factors of local operators in the repulsive Lieb–Liniger model at finite size. These are essential ingredients for both numerical and analytical calculations. From the theory of algebraic Bethe ansatz, it is known that the form factors of local operators satisfy a particular type of recursive relations. We show that in some cases these relations can be used directly to derive practical expressions in terms of the determinant of a matrix whose dimension scales linearly with the system size. Our main results are determinant formulas for the form factors of the operators and ΨR(0), for arbitrary integer R, where Ψ, are the usual field operators. From these expressions, we also derive the infinite size limit of the form factors of these local operators in the attractive regime.

Spinoza for Our Time: Politics and Postmodernity by Antonio Negri (review)

Reviewed by: Spinoza for Our Time: Politics and Postmodernity by Antonio Negri Heather Ashley Hayes Antonio Negri, Spinoza for Our Time: Politics and Postmodernity New York: Columbia University Press, 2013, 152 pp. Gilles Deleuze, writing in 2000 about Antonio Negri’s work The Savage Anomaly, argued, “Antonio Negri is authentically and profoundly Spinozian.” Negri had authored Anomaly, his first work dedicated to Baruch Spinoza’s place in philosophy, in prison in 1991 while awaiting trial on the false charge that he instigated the Red Brigades’ assassination of former Italian Prime Minister Aldo Moro. In 2004, Negri wrote Subversive Spinoza, extending his work in Savage Anomaly and continuing his radical renewal of Marxism via new readings of the challenging metaphysics of Spinoza. His third, less ambitious yet piercingly insightful work on Spinoza, Spinoza for Our Time: Politics and Postmodernity, further nuances these previous readings. Negri is not the first to champion a materialist Spinoza. The foundations of this inquiry were laid in part by Deleuze himself publishing Expressionism in Philosophy: Spinoza in 1968 while in 1969 Alexandre Martheron published Individu et communauté chez Spinoza, both texts arguing for serious readings of Spinoza into political philosophy. Deleuze combed the western philosophical tradition for alternatives to Hegel, and found important possibilities in Spinoza. While Louis Althusser wrote little on Spinoza directly, the influence of the philosopher is evident in the work of his students Etienne Balibar and Pierre Macherey, both of whom have penned influential work on Spinoza. As Eugene Holland points out, Macherey’s work frames [End Page 415] “a direct confrontation between Spinoza and Hegel, stressing the degree to which the former eludes the grasp of the latter’s history of philosophy, and therefore represents an important alternative to Hegelian views” (Eugene Holland, “Spinoza and Marx,” Cultural Logic 2, 1 [Fall 1998]). In the first book of Cahiers Spinoza, published in 1977, Maximilian Rubel, Martheron, and Albert Igoin all confront the possibility of Spinoza’s influence on Karl Marx. Particularly, they focus on extensive passages of Spinoza’s Tractatus Theologico-Politicus found hand-copied into Karl Marx’s early notebooks. As Eugene Holland argues, alternatives to Hegel and Hegelian Marxism are desirable for this group of philosophers, of which Negri is perhaps the most enthusiastic. For Althusser, alternatives to Hegelian Marxism became attractive as weapons in the fight against Stalinism within the French Communist Party. For Deleuze and many poststructuralists, Nietzsche (who acknowledged Spinoza’s influence), proved attractive because his method differed markedly from Hegel’s, and to some extent Marx’s. As Holland notes, More generally, the impetus to reevaluate Hegelian Marxism in France arose in response to a number of post-war developments, in the fields of politics and academics alike: the decline of the French working class as a “class-conscious” political actor, and of the French Communist Party as its “revolutionary” vanguard, in Fifth Republic politics and society; but also the demise of Soviet and Chinese Communisms as viable or attractive Marx-inspired regimes; and within academics, the growing dissatisfaction with certain Hegelian elements of Marxism, among historians as well as philosophers themselves. (Holland, “Spinoza and Marx”) Holland helpfully recalls the importance that interpretations of the French Revolution of 1789 took on in disputes among historians, some of whom sought to revise Marxist takes on 1789 as a bourgeois revolution that would serve to spur a future, more proletarian one. For materialist historians, Holland argues, “the problem, in short, was how to square the actual diversity of motives and actions of particular French merchants, lawyers, and statesmen with the unifying notion of the bourgeoisie as a class acting as a (singular) political agent in the historical field.” Here, Spinozan materialism, read as a forerunner to Marx’s materialism, can eradicate Hegelian dialectics. For Negri’s work, the central goal has been to read Spinozan materialism as a mature precursor to Marx’s own materialism and as a result, to relate Spinoza’s central relevance for contemporary Marxism as a true materialist. In Savage Anomaly he noted, “Spinoza’s materialist metaphysics is the potent anomaly of the century: not a vanquished or marginal anomaly but, rather, an anomaly of victorious materialism, of the ontology of a being that...

From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces

Using all-atom molecular dynamics (MD) simulations at constant water chemical potential in combination with basic theoretical arguments, we study hydration-induced interactions between two overall charge-neutral yet polar planar surfaces with different wetting properties. Whether the water film between the two surfaces becomes unstable below a threshold separation and cavitation gives rise to long-range attraction, depends on the sum of the two individual surface contact angles. Consequently, cavitation-induced attraction also occurs for a mildly hydrophilic surface interacting with a very hydrophobic surface. If both surfaces are very hydrophilic, hydration repulsion dominates at small separations and direct attractive force contribution can-if strong enough-give rise to wet adhesion in this case. In between the regimes of cavitation-induced attraction and hydration repulsion we find a narrow range of contact angle combinations where the surfaces adhere at contact in the absence of cavitation. This dry adhesion regime is driven by direct surface-surface interactions. We derive simple laws for the cavitation transition as well as for the transition between hydration repulsion and dry adhesion, which favorably compare with simulation results in a generic adhesion state diagram as a function of the two surface contact angles.

Multiple signatures of topological transitions for interacting fermions in chain lattices

We study one-component fermions in chain lattices with proximity-induced superconducting gap and interparticle short-range interaction, capable of hosting Majorana fermions. By systematically tracking various physical quantities, we show that topological states and topological phase transitions in the system can be identified by multiple signatures in thermodynamic quantities and pair-condensate properties, in good agreement with the known signatures in the ground-state energy and entanglement spectrum. We find the disappearance of the topological phase in a largely attractive regime, in which the system undergoes a first-order transition between two topologically trivial states. In addition, the stability of the signatures against finite size, disorder, and inhomogeneity is analyzed. Our results provide additional degrees of freedom for the characterization of topological states with interaction and for the experimental detection of emergent Majorana fermions.