Geometric Entropy Research Articles

Dynamics and the Godbillon–Vey class of $C^1$ foliations

Let $\mathcal{F}$ be a codimension-one, $C^2$-foliation on a manifold $M$ without boundary. In this work we show that if the Godbillon–Vey class $GV(\mathcal{F}) \in H^3(M)$ is non-zero, then $\mathcal{F}$ has a hyperbolic resilient leaf. Our approach is based on methods of $C^1$-dynamical systems, and does not use the classification theory of $C^2$-foliations. We first prove that for a codimension-one $C^1$-foliation with non-trivial Godbillon measure, the set of infinitesimally expanding points $E(\mathcal{F})$ has positive Lebesgue measure. We then prove that if $E(\mathcal{F})$ has positive measure for a $C^1$-foliation, then $\mathcal{F}$ must have a hyperbolic resilient leaf, and hence its geometric entropy must be positive. The proof of this uses a pseudogroup version of the Pliss Lemma. The first statement then follows, as a $C^2$-foliation with non-zero Godbillon–Vey class has non-trivial Godbillon measure. These results apply for both the case when $M$ is compact, and when $M$ is an open manifold.

Constructing entanglement wedges for Lifshitz spacetimes with Lifshitz gravity

Holographic relationships between entanglement entropy on the boundary of a spacetime and the area of minimal surfaces in the bulk provide an important entry in the bulk/boundary dictionary. While constructing the necessary causal and entanglement wedges is well understood in asymptotically AdS spacetimes, less is known about the equivalent constructions in spacetimes with different asymptotics. In particular, recent attempts to construct entanglement and causal wedges for asymptotically Lifshitz solutions in relativistic gravitational theories have proven problematic. We note a simple observation, that a Lifshitz bulk theory, specifically a covariant formulation of Ho\v{r}ava-Lifshitz gravity coupled to matter, has causal propagation defined by Lifshitz modes. We use these modes to construct causal and entanglement wedges and compute the geometric entanglement entropy, which in such a construction matches the field theory prescription.

The Simplest Non-Expected Utility Model for Lottery and Portfolio Choices

Abstract This paper explores a particularly simple model of choice under risk, based on geometric means and entropy. Despite its simplicity, it satisfies various prudence and risk aversion conditions, is consistent with the Allais paradox, and generates various insurance-related results. Within a portfolio framework with compounded reinvestments, our index fits the risks/rewards data from post-war US stock market returns and recent international markets, at least as well as does the standard deviation measures more typically used. It also generates returns that are consistent with the equity premium puzzle.

Topological entropy and geometric entropy and their application to the horizontal visibility graph for financial time series

In this paper, we introduce topological entropy (TE) based on time series, which characterizes the total exponential complexity of a quantified system with a single number. Combined with multiscale theory, we propose geometric entropy (GE), aiming to examine the correlation among different time series. In order to detect the properties of TE and GE, we apply them to an original symbolic method utilized to measure time series irreversibility, namely horizontal visibility algorithm. On this basis, we propose a time series irreversibility measure, i.e., normalized index. Then, we employ TE and GE based on the horizontal visibility graph symbolic algorithm to simulated time series, which is generated by the logistic map with different parameters. Through the comparison of the results, we find out that different simulated data have the same variation tendency of TE, which means that TE is capable of reflecting the similarity among different time series. On the basic of these results, we further analyze the irreversibility of simulated data and also get some interesting findings. From the GE results comparison, we conclude that the GE method can distinguish different time series and expose their correlation efficiently. As a farther validation, we explore the effects of these methods on the analysis of different stock time series. Results show that they can reflect a large number of interrelationships, and successfully quantify the changes in the complexity of different stock market data.

Quantum chemical study on the X-H…H-M (X=-C2 H, -C2 H3 and M=Li, Na, K, Fe, Zn) dihydrogen bond systems

The structure and electronic properties of dihydrogen bond complexes that form between H of M-H (where M-H=LiH, NaH, KH, FeH2 and ZnH2) and H of acetylene HC ≡ CH and H of ethylene HCH=HCH compounds was predicted employing density functional theory. The ground state dihydrogen bond complexes were optimized at B3LYP/6–311++G** level of theory. The geometrical parameters, energies, entropies and AIM analysis of the considered complexes were calculated and analyzed

Entropy in Born-Infeld gravity

There is a class of higher derivative gravity theories that are in some sense natural extensions of cosmological Einstein's gravity with a unique maximally symmetric classical vacuum and only a massless spin-2 excitation about the vacuum and no other perturbative modes. These theories are of the Born-Infeld determinantal form. We show that the macroscopic dynamical entropy as defined by Wald for bifurcate Killing horizons in these theories are equivalent to the geometric Bekenstein-Hawking entropy (or more properly Gibbons-Hawking entropy for the case of de Sitter spacetime) but given with an effective gravitational constant which encodes all the information about the background spacetime and the underlying theory. We also show that the higher curvature terms increase the entropy. We carry out the computations in generic n-dimensions including the particularly interesting limits of three, four and infinite number of dimensions. We also give a preliminary discussion about the black hole entropy in generic dimensions for the BI theories.

Topological network entanglement as order parameter for the emergence of geometry

We show that, in discrete models of quantum gravity, emergent geometric space can be viewed as the entanglement pattern in a mixed quantum state of the ‘universe’, characterized by a universal topological network entanglement. As a concrete example we analyze the recently proposed model in which geometry emerges due to the condensation of 4-cycles in random regular bipartite graphs, driven by the combinatorial Ollivier–Ricci curvature. Using this model we show that the emergence of geometric order decreases the entanglement entropy of random configurations. The lowest geometric entanglement entropy is realized in four dimensions.

Catching homologies by geometric entropy

A geometric entropy is defined in terms of the Riemannian volume of the parameter space of a statistical manifold associated with a given network. As such it can be a good candidate for measuring networks complexity. Here we investigate its ability to single out topological features of networks proceeding in a bottom-up manner: first we consider small size networks by analytical methods and then large size networks by numerical techniques. Two different classes of networks, the random graphs and the scale-free networks, are investigated computing their Betti numbers and then showing the capability of geometric entropy of detecting homologies.

Geometric entanglement in the Laughlin wave function

We study numerically the geometric entanglement in the Laughlin wave function, which is of great importance in condensed matter physics. The Slater determinant having the largest overlap with the Laughlin wave function is constructed by an iterative algorithm. The logarithm of the overlap, which is a geometric quantity, is then taken as a geometric measure of entanglement. It is found that the geometric entanglement is a linear function of the number of electrons to a good extent. This is especially the case for the lowest Laughlin wave function, namely the one with filling factor of 1/3. Surprisingly, the linear behavior extends well down to the smallest possible value of the electron number, namely, N = 2. The constant term does not agree with the expected topological entropy. In view of previous works, our result indicates that the relation between geometric entanglement and topological entropy is very subtle.

On the degenerate and non-degenerate two-photon interaction between a two-level atom and a quantized two-modes: Entanglement and Pancharatnam phase

In this paper, we study the interaction between a two-level atom and a three types of nonlinear interaction of two modes, two as a degenerate two photon and the third of the converter form. The solution to the Schrodinger equation is obtained exactly under a certain specific condition. By using this solution we discuss numerically the atomic inversion, the degree of entanglement through the atomic Wehrl entropy, the geometric phase entropy for chosen values of the detuning and coupling parameters. Statistical properties of the investigated system is discussed by the evolution of the Mandel parameter.

Influence of Formation Conditions on the Level of Arrays Ordering of Anodic Titanium Oxide Nanotubes

Nanotubular titanium oxide coatings with different morphology and dimensional parameters are formed by anodic oxidation under different voltage and time modes in fluorine aqueous-nonaqueous electrolytes containing glycerin as well as several surface-active agents (SAA). Their morphological peculiarities are examined and qualitative and quantitative analysis of obtained types of ordering is carried out, geometric configuration entropy are calculated on the base of analysis SEM images and theory of self-organization.

Geometric entropy and edge modes of the electromagnetic field

We calculate the vacuum entanglement entropy of Maxwell theory in a class of curved spacetimes by Kaluza-Klein reduction of the theory onto a two-dimensional base manifold. Using two-dimensional duality, we express the geometric entropy of the electromagnetic field as the entropy of a tower of scalar fields, constant electric and magnetic fluxes, and a contact term, whose leading-order divergence was discovered by Kabat. The complete contact term takes the form of one negative scalar degree of freedom confined to the entangling surface. We show that the geometric entropy agrees with a statistical definition of entanglement entropy that includes edge modes: classical solutions determined by their boundary values on the entangling surface. This resolves a long-standing puzzle about the statistical interpretation of the contact term in the entanglement entropy. We discuss the implications of this negative term for black hole thermodynamics and the renormalization of Newton's constant.

Generalized second law of thermodynamics in f ( R , T ) $f(R,T)$ theory of gravity

We present a study of the generalized second law of thermodynamics in the scope of the f(R,T) theory of gravity, with R and T representing the Ricci scalar and trace of the energy-momentum tensor, respectively. From the energy-momentum tensor equation for the f(R,T) = R + f(T) case, we calculate the form of the geometric entropy in such a theory. Then, the generalized second law of thermodynamics is quantified and some relations for its obedience in f(R,T) gravity are presented. Those relations depend on some cosmological quantities, as the Hubble and deceleration parameters, and on the form of f(T).

Information entropy of coding metasurface.

Because of their exceptional capability to tailor the effective medium parameters, metamaterials have been widely used to control electromagnetic waves, which has led to the observation of many interesting phenomena, for example, negative refraction, invisibility cloaking, and anomalous reflections and transmissions. However, the studies of metamaterials or metasurfaces are mainly limited to their physical features; currently, there is a lack of viewpoints on metamaterials and metasurfaces from the information perspective. Here we propose to measure the information of a coding metasurface using Shannon entropy. We establish an analytical connection between the coding pattern of an arbitrary coding metasurface and its far-field pattern. We introduce geometrical entropy to describe the information of the coding pattern (or coding sequence) and physical entropy to describe the information of the far-field pattern of the metasurface. The coding metasurface is demonstrated to enhance the information in transmitting messages, and the amount of enhanced information can be manipulated by designing the coding pattern with different information entropies. The proposed concepts and entropy control method will be helpful in new information systems (for example, communication, radar and imaging) that are based on the coding metasurfaces.

Hagedorn transition and topological entanglement entropy

Induced by the Hagedorn instability, weakly-coupled U(N) gauge theories on a compact manifold exhibit a confinement/deconfinement phase transition in the large-N limit. Recently we discover that the thermal entropy of a free theory on S3 gets reduced by a universal constant term, −N2/4, compared to that from completely deconfined colored states. This entropy deficit is due to the persistence of Gauss's law, and actually independent of the shape of the manifold. In this paper we show that this universal term can be identified as the topological entangle entropy both in the corresponding 4+1D bulk theory and the dimensionally reduced theory. First, entanglement entropy in the bulk theory contains the so-called “particle” contribution on the entangling surface, which naturally gives rise to an area-law term. The topological term results from the Gauss's constraint of these surface states. Secondly, the high-temperature limit also defines a dimensionally reduced theory. We calculate the geometric entropy in the reduced theory explicitly, and find that it is given by the same constant term after subtracting the leading term of O(β−1). The two procedures are then applied to the confining phase, by extending the temperature to the complex plane. Generalizing the recently proposed 2D modular description to an arbitrary matter content, we show the leading local term is missing and no topological term could be definitely isolated. For the special case of N=4 super Yang–Mills theory, the results obtained here are compared with that at strong coupling from the holographic derivation.

Entropy of foliations with leafwise Finsler structure

We extend the notion of the geometric entropy of foliation to foliated manifolds equipped with leafwise Finsler structure. We study the relation between the geometric entropy and the topological entropy of the holonomy pseudogroup. The case of a foliated manifold with leafwise Randers structure is considered. In this case the estimates for one dimensional foliation defined by a vector field in terms of the topological entropy of a flow are presented.

Geometric Entropy for Lead vs Top-Rope Rock Climbing

Geometric Entropy for Lead vs Top-Rope Rock Climbing

The Effect of Magnesium Carbonate (Chalk) on Geometric Entropy, Force, and Electromyography During Rock Climbing.

Rock climbers believe chalk dries the hands of sweat and improves the static coefficient of friction between the hands and the surface of the rock. The purpose of this study was to assess whether chalk affects geometric entropy or muscular activity during rock climbing. Nineteen experienced recreational rock climbers (13 males, 6 females; 173.5 ± 7.0 cm; 67.5 ± 3.4 kg) completed 2 climbing trails with and without chalk. The body position of the climber and muscular activity of the finger flexors was recorded throughout the trial. Following the movement sequence participants hung from a standard climbing hold until they slipped from the climbing structure, while the coefficient of friction and the ratio of the vertical forces on the hands and feet were determined. Although there were no differences in the coefficient of friction (P = .748), geometric entropy (P = .359), the ratio of the vertical forces between the hands and feet (P = .570), or muscular activity (P = .968), participants were able to hang longer after the use of chalk 62.9 ± 36.7 s and 49.3 ± 25.2 s (P = .046). This is advantageous because it may allow for prolonged rests, and more time to plan the next series of climbing moves.

Gaussian Network’s Dynamics Reflected into Geometric Entropy

We consider a geometric entropy as a measure of complexity for Gaussian networks, namely networks having Gaussian random variables sitting on vertices and their correlations as weighted links. We then show how the network dynamics described by the well-known Ornstein–Uhlenbeck process reflects into such a measure. We unveil a crossing of the entropy time behaviors between switching on and off links. Moreover, depending on the number of links switched on or off, the entropy time behavior can be non-monotonic.

A geometric entropy detecting the Erdös-Rényi phase transition

We propose a method to associate a differentiable Riemannian manifold to a generic many-degrees-of-freedom discrete system which is not described by a Hamiltonian function. Then, in analogy with classical statistical mechanics, we introduce an entropy as the logarithm of the volume of the manifold. The geometric entropy so defined is able to detect a paradigmatic phase transition occurring in random graphs theory: the appearance of the “giant component” according to the Erdös-Rényi theorem.