Systems Of Arbitrary Dimension Research Articles

Symmetries of Thirring Models on 3D Lattices

We review some recent developments about strongly interacting relativistic Fermi theories in three spacetime dimensions. These models realize the asymptotic safety scenario and are used to describe the low-energy properties of Dirac materials in condensed matter physics. We begin with a general discussion of the symmetries of multi-flavor Fermi systems in arbitrary dimensions. Then we review known results about the critical flavor number Ncrit of Thirring models in three dimensions. Only models with a flavor number below Ncrit show a phase transition from a symmetry-broken strong-coupling phase to a symmetric weak-coupling phase. Recent simulations with chiral fermions show that Ncrit is smaller than previously extracted with various non-perturbative methods. Our simulations with chiral SLAC fermions reveal that for four-component flavors Ncrit=0.80(4). This means that all reducible Thirring models with Nr=1,2,3,… show no phase transition with order parameter. Instead, we discover footprints of phase transitions without order parameter. These new transitions are probably smooth and could be used to relate the lattice Thirring models to Thirring models in the continuum. For a single irreducible flavor, we provide previously unpublished values for the critical couplings and critical exponents.

Experimental observation of a quadrupolar phase via quench dynamics on a spin simulator

Recently, higher-order topological insulators have drawn much attention from researchers. For chiral-symmetric one-dimensional systems, the mean chiral displacement, a bulk observable related to the topological invariant, can distinguish topological states from trivial phases. Naturally, there exists an analogous quality for the higher-order one. In a previous work [T. Mizoguchi, Y. Kuno, and Y. Hatsugai, Phys. Rev. Lett. 126, 016802 (2021)], the mean chiral quadrupole moment is introduced. Inspired by this work, we investigate the quadrupolar phase of a higher-order topological insulator on a spin quantum simulator. With focus on a two-particle noninteracting Benalcazar-Bernevig-Hughes model, by changing the amplitude of hopping interactions, we first observe quantum phase transitions from topological phase to trivial phase using a spin simulator experimentally. Since the mean chiral quadrupole moment has robustness against environmental noise, we also test its dependence on perturbations. As an exploration of the bulk observable of a higher-order topological insulator, it may provide one path to investigate arbitrary dimensional systems.

Adaptive quantum state tomography via weak value

Quantum state tomography strategy via weak value is valid for arbitrary dimensional systems, and can be easily realized. However, the efficiency of quantum state tomography strategy via weak value is lower than that of the conventional quantum state tomography (QST), especially for high-dimensional systems. To improve the efficiency of the scheme, we propose a two-step adaptive quantum state tomography via weak value for pure states (AQSTW). In AQSTW, by using appropriate measurement strength, the efficiency of AQSTW is significantly larger than that of the conventional QST, especially for high-dimensional systems. And AQSTW can be easily implemented. These results demonstrate AQSTW may be useful in the measurements of the unknown quantum states.

Witnessing negative conditional entropy

Quantum states that possess negative conditional von Neumann entropy provide quantum advantage in several information-theoretic protocols including superdense coding, state merging, distributed private randomness distillation, and one-way entanglement distillation. While entanglement is an important resource, only a subset of entangled states have negative conditional von Neumann entropy. In this work, we characterize the class of density matrices having non-negative conditional von Neumann entropy as convex and compact. This allows us to prove the existence of a Hermitian operator (a witness) for the detection of states having negative conditional entropy for bipartite systems in arbitrary dimensions. We show two constructions of such witnesses. For one of the constructions, the expectation value of the witness in a state is an upper bound to the conditional entropy of the state. We pose the problem of obtaining a tight upper bound to the set of conditional entropies of states in which an operator gives the same expectation value. We solve this convex optimization problem numerically for a two qubit case and find that this enhances the usefulness of our witnesses. We also find that for a particular witness, the estimated tight upper bound matches the value of conditional entropy for Werner states. We explicate the utility of our work in the detection of useful states in several protocols.

Effects of white noise on the violation of Bell-type inequalities based on probability theory

We introduce two types of statistical quasi-separation between local observables to construct two-party Bell-type inequalities for an arbitrary dimensional systems and arbitrary number of measurement settings per site. Note that, the main difference between statistical quasi-separations and the usual statistical separations is that the former are not symmetric under exchange of the two local observables, whereas latter preserve the symmetry. We show that a variety of Bell inequalities can be derived by sequentially applying triangle inequalities which statistical quasi-separations satisfy. A sufficient condition is presented to show quantum violations of the Bell-type inequalities with infinitesimal values of critical visibility v c.

Phonon Casimir effect in polyatomic systems

The phonon Casimir effect describes the phonon-mediated interaction between defects in condensed-matter systems. Using the path-integral formalism, we derive a general method for calculating the Helmholtz free energy due to vibrational modes in systems of arbitrary dimensionality and composition. Our results make it possible to extract the defect interaction energy at any temperature for various defect configurations. We demonstrate our approach in action by performing numerical calculations for mono- and diatomic chains, as well as a diatomic molecule, at zero and finite temperatures and validate our results using exact diagonalization.

Entanglement of formation and monogamy of multi-party quantum entanglement

We provide a sufficient condition for the monogamy inequality of multi-party quantum entanglement of arbitrary dimensions in terms of entanglement of formation. Based on the classical–classical–quantum(ccq) states whose quantum parts are obtained from the two-party reduced density matrices of a three-party quantum state, we show the additivity of the mutual information of the ccq states guarantees the monogamy inequality of the three-party pure state in terms of EoF. After illustrating the result with some examples, we generalize our result of three-party systems into any multi-party systems of arbitrary dimensions.

Shrinking targets for non-autonomous systems

In the present work we establish a Bowen-type formula for the Hausdorff dimension of shrinking target sets for non-autonomous conformal iterated function systems in arbitrary dimensions and satisfying certain conditions. In the case of dimension 1 we also investigate non-linear perturbations of linear systems and obtain sufficient conditions under which the perturbed systems satisfy the conditions in our hypotheses.

Affine formation maneuver control of high-order multi-agent systems over directed networks

To drive a group of agents to maneuver continuously with the desired collective forms, this paper addresses a distributed formation maneuver control problem of directed networked high-order multi-agent systems in arbitrary dimensions. Unlike the conventional methods where the target formation is time invariant, we propose an affine formation method based on the properties of affine transformation, in which the target formation can be time-varying and affinely transformed from the given nominal formation. This paper provides and proves a sufficient and necessary condition of achieving the directed graphical affine localizability, and it only needs that the leaders have a generic configuration and the followers are accessible to the subset of leaders. To achieve the whole formation maneuvers, assume that the leaders decide the whole formation’s maneuver actions, then the control algorithms of the arbitrary-order integrator followers are proposed to track the time-varying target formation and the global convergence of tracking errors is also proved. Furthermore, this paper studies the practical problems of formation maneuvers when existing non-uniform time delays. Finally, both two-dimensional and three-dimensional simulation examples are given to demonstrate the effectiveness of theoretical results.

Efficient quantum simulation for thermodynamics of infinite-size many-body systems in arbitrary dimensions

In this work we propose to simulate many-body thermodynamics of infinite-size quantum lattice models in one, two, and three dimensions, in terms of few-body models of only O(10) sites, which we coin as quantum entanglement simulators (QES's). The QES is described by a temperature-independent Hamiltonian, with the boundary interactions optimized by the tensor network methods to mimic the entanglement between the bulk and environment in a finite-size canonical ensemble. The reduced density matrix of the physical bulk then gives that of the infinite-size canonical ensemble under interest. We show that the QES can, for instance, accurately simulate varieties of many-body phenomena, including finite-temperature crossover and algebraic excitations of the one-dimensional spin liquid, the phase transitions and low-temperature physics of the two- and three-dimensional antiferromagnets, and the crossovers of the two-dimensional topological system. Our work provides an efficient way to explore the thermodynamics of intractable quantum many-body systems with easily accessible systems.

New and Future Developments in Microbial Biotechnology and Bioengineering: From Cellulose to Cellulase: Strategies to Improve Biofuel Production

Morphological changes in a material are a result of the evolution of its interfaces due to applied or capillary forces. Morphological changes occur by capillary forces if the motion acts to decrease the total free energy associated with the interfaces in the system. For isotropic systems with a single type of interface, the interfacial area always tends toward a minimum. On the other hand, for anisotropic surfaces, the interfacial area could increase during minimization of free energy, via a process known as faceting. The von Neumann-Mullins criterion for two-dimensional grain growth states that grains with fewer than six edges will shrink and eventually disappear, whereas grains with greater than six edges will grow. Grains with exactly six edge are dimensionally stable and will neither grow nor shrink. The von Neumann-Mullins approach has recently been generalized for systems of arbitrary dimensionality by MacPherson and Srolovitz. Diffusional creep results in permanent deformation of the material as a result of capillary and applied forces. There are two types of diffusional creep: Nabarro-Herring creep happens when the mass flux occurs via the crystalline matrix, and Coble creep occurs when the mass flux is along the grain boundaries. Sintering is the process by which a compressed powder or granular material undergoes neck growth and densification through heat treatment. This heat treatment is not hot enough to induce melting, and it is usually conducted under pressure to aid in the sintering process. The final sintered body has a lower porosity and greater mechanical integrity compared to the initial green body. Recently, cold sintering techniques have leveraged chemical reactions to promote effective sintering of ceramics at much lower temperatures compared to traditional processes.

Causation and information flow with respect to relative entropy.

Recently, a rigorous formalism has been established for information flow and causality within dynamical systems with respect to Shannon entropy. In this study, we re-establish the formalism with respect to relative entropy, or Kullback-Leiber divergence, a well-accepted measure of predictability because of its appealing properties such as invariance upon nonlinear transformation and consistency with the second law of thermodynamics. Different from previous studies (which yield consistent results only for 2D systems), the resulting information flow, say T, is precisely the same as that with respect to Shannon entropy for systems of arbitrary dimensionality, except for a minus sign (reflecting the opposite notion of predictability vs. uncertainty). As before, T possesses a property called principle of nil causality, a fact that classical formalisms fail to verify in many situation. Besides, it proves to be invariant upon nonlinear transformation, indicating that the so-obtained information flow should be an intrinsic physical property. This formalism has been validated with the stochastic gradient system, a nonlinear system that admits an analytical equilibrium solution of the Boltzmann type.

Projective synchronization of a class of chaotic systems by dynamic feedback control method

This paper investigates the projective synchronization problem of a class of chaotic systems in arbitrary dimensions. Firstly, a necessary and sufficient condition for the existence of the projective synchronization problem is presented. And this condition is equivalent to check whether a group of algebraic equations about $$\alpha $$ have solutions or not. Secondly, an algorithm is proposed to obtain all the solutions of the projective synchronization problem. Thirdly, a simple and physically implementable controller is designed to ensure the realization of the projective synchronization. Finally, three numerical examples are provided to verify the effectiveness and the validity of the proposed results.

On the effective potential of Duru-Kleinert path integrals

We propose a new method to evaluate the effective potential in the path integral for the fixed-energy amplitude as well as for the pseudotime evolution kernel in the formalism by Duru and Kleinert. Restriction to the postpoint or the prepoint prescriptions in formulating time sliced path integrals is avoided by leaving off the use of expectation values for correction terms. This enables us to consider an arbitrary ordering prescription and to examine the ordering dependence of the effective potential. To investigate parameter dependences, we introduce the ordering parameter α in addition to the splitting parameter λ in the formulation of the time sliced path integral. The resulting path integrals are found to be independent of the ordering parameter although the explicit dependence, given by a contribution proportional to (1−2λ)2, on the splitting parameter remains. As an application, we check the relationship between path integrals for the radial oscillator and the radial Coulomb system in arbitrary dimensions.

Quantum canonical ensemble: A projection operator approach

Knowing the exact number of particles N, and taking this knowledge into account, the quantum canonical ensemble imposes a constraint on the occupation number operators. The constraint particularly hampers the systematic calculation of the partition function and any relevant thermodynamic expectation value for arbitrary but fixed N. On the other hand, fixing only the average number of particles, one may remove the above constraint and simply factorize the traces in Fock space into traces over single-particle states. As is well known, that would be the strategy of the grand-canonical ensemble which, however, comes with an additional Lagrange multiplier to impose the average number of particles. The appearance of this multiplier can be avoided by invoking a projection operator that enables a constraint-free computation of the partition function and its derived quantities in the canonical ensemble, at the price of an angular or contour integration.Introduced in the recent past to handle various issues related to particle-number projected statistics, the projection operator approach proves beneficial to a wide variety of problems in condensed matter physics for which the canonical ensemble offers a natural and appropriate environment. In this light, we present a systematic treatment of the canonical ensemble that embeds the projection operator into the formalism of second quantization while explicitly fixing N, the very number of particles rather than the average. Being applicable to both bosonic and fermionic systems in arbitrary dimensions, transparent integral representations are provided for the partition function ZN and the Helmholtz free energy FN as well as for two- and four-point correlation functions. The chemical potential is not a Lagrange multiplier regulating the average particle number but can be extracted from FN+1−FN, as illustrated for a two-dimensional fermion gas.

On static solutions of the Einstein-Scalar Field equations

In this article we study self-gravitating static solutions of the Einstein-Scalar Field system in arbitrary dimensions. We discuss the existence of geodesically complete solutions depending on the form of the scalar field potential \(V(\phi )\), and provide full global geometric estimates when the solutions exist. The most complete results are obtained for the physically important Klein–Gordon field and are summarised as follows. When \(V(\phi )=m^{2}|\phi |^{2}\), it is proved that geodesically complete solutions have Ricci-flat spatial metric, have constant lapse and are vacuum, (that is \(\phi \) is constant and equal to zero if \(m\ne 0\)). In particular, when the spatial dimension is three, the only such solutions are either Minkowski or a quotient thereof (no nontrivial solutions exist). When \(V(\phi )=m^{2}|\phi |^{2}+2\Lambda \), that is, when a vacuum energy or a cosmological constant is included, it is proved that no geodesically complete solution exists when \(\Lambda >0\), whereas when \(\Lambda <0\) it is proved that no non-vacuum geodesically complete solution exists unless \(m^{2}<-2\Lambda /(n-1)\), (n is the spatial dimension) and the spatial manifold is non-compact. The proofs are based on novel techniques in comparison geometry a la Bakry-Emery that have their own interest.

Certifying Einstein-Podolsky-Rosen steering via the local uncertainty principle

Uncertainty principle lies at the heart of quantum mechanics, while nonlocality is an intriguing phenomenon of quantum mechanics to rule out local causal theories. One subtle form of nonlocality is so-called Einstein-Podolsky-Rosen (EPR) steering, which holds the potential for shared entanglement verification even if the one-sided measurement device is untrusted. However, certifying EPR steering remains a big challenge presently. Here, we employ the local uncertainty relation to provide an experimental friendly approach for EPR steering verification. We show that the strength of EPR steering is quantitatively linked to the strength of the uncertainty relation, as well as the amount of entanglement. We find also that the realignment method works for detecting EPR steering of an arbitrary dimensional system.

Do spins have directions?

The standard Bloch sphere representation has been recently generalized to describe not only systems of arbitrary dimension, but also their measurements, in what has been called the extended Bloch representation of quantum mechanics. This model, which offers a solution to the longstanding measurement problem, is based on the hidden-measurement interpretation of quantum mechanics, according to which the Born rule results from our lack of knowledge of the measurement interaction that each time is actualized between the measuring apparatus and the measured entity. In this article, we present the extended Bloch model and use it to investigate, more specifically, the nature of the quantum spin entities and of their relation to our three-dimensional Euclidean theater. Our analysis shows that spin eigenstates cannot generally be associated with directions in the Euclidean space, but only with generalized directions in the Blochean space, which apart from the special case of spin one-half entities, is a space of higher dimensionality. Accordingly, spin entities have to be considered as genuine non-spatial entities. We also show, however, that specific vectors can be identified in the Blochean theater that are isomorphic to the Euclidean space directions, and therefore representative of them, and that spin eigenstates always have a predetermined orientation with respect to them. We use the details of our results to put forward a new view of realism, that we call multiplex realism, providing a specific framework with which to interpret the human observations and understanding of the component parts of the world. Elements of reality can be represented in different theaters, one being our customary Euclidean space, and another one the quantum realm, revealed to us through our sophisticated experiments, whose elements of reality, in the quantum jargon, are the eigenvalues and eigenstates. Our understanding of the component parts of the world can then be guided by looking for the possible connections, in the form of partial morphisms, between the different representations, which is precisely what we do in this article with regard to spin entities.

Classifying and quantifying basins of attraction.

A scheme is proposed to classify the basins for attractors of dynamical systems in arbitrary dimensions. There are four basic classes depending on their size and extent, and each class can be further quantified to facilitate comparisons. The calculation uses a Monte Carlo method and is applied to numerous common dissipative chaotic maps and flows in various dimensions.

Energy flow in quantum critical systems far from equilibrium

Gauge/gravity duality is normally reserved for the study of black holes, but it can be applied to the study of out-of-equilibrium quantum systems in arbitrary dimension.