Reflection-less device allows electromagnetic warp drive

One of the striking properties of artificially structured materials is the negative refraction, an optical feature that known natural materials do not exhibit. Here, we propose a simple design, composed of two parallel layers of materials with different refraction indices $n_1=-n_2$, that constructs perfect reflection-less devices. The electromagnetic waves can tunnel from one layer to the other, a feature that resembles a truncation of the physical space leading to an electromagnetic warp drive. Since the refractive indices do not require any large values, this method demonstrates for the first time the practical feasibility of guiding electromagnetic fields in complete absence of reflection phenomena and without degradation of transmission efficiency at all.Comment: 8 pages, 7 figure

Inversible Max-Plus Algebras and Integrable systems

We present an extended version of max-plus algebra which includes the inverse operator of "max". This algebra enables us to ultra-discretize the system including subtractions and obtain new ultra-discrete equations. The known ultra-discrete equations can also be recovered by this construction.Comment: 21 page

Correlated Emission of Hadrons from Recombination of Correlated Partons

We discuss different sources of hadron correlations in relativistic heavy ion collisions. We show that correlations among partons in a quasi-thermal medium can lead to the correlated emission of hadrons by quark recombination and argue that this mechanism offers a plausible explanation for the dihadron correlations in the few GeV/c momentum range observed in Au+Au collisions at RHIC.Comment: 4 pages, 2 figures; v2: typo on p.4 correcte

Unveiling the directional network behind the financial statements data using volatility constraint correlation

Financial data, such as financial statements, stores valuable and critical information to potentially assist stakeholders and investors optimize their capital so that it maximizes overall economic growth. Since there are many variables in financial statements, it is important to determine the causal relationships, that is, the directional influence between them in a structural way, as well as to understand the related accounting mechanisms. However, the analysis of variable-to-variable relationships in financial information by using the standard correlation functions is not sufficient to unveil directionality. Here, we use the volatility constrained correlation (VC correlation) method that enables us to predict the directional relationship between the two variables. To be precise, we apply the VC correlation method to five major financial information variables (revenue, net income, operating income, own capital and market capitalization) of 2321 firms in 28 years from 1990 to 2018 listed on Tokyo Stock Exchange in order to identify which variables are influential and which are susceptible variables. Our findings show that operating income is the most influential variable and market capital and revenue are the most susceptible variables among the five major accounting variables. Surprisingly, the results are different from the existing intuitive understanding suggested by widely used investment strategy indicators known as PER and PBR, which report that net income and own capital are the most influential variable on market capital. Taken together, the presented analysis may assist managers, stakeholders and investors to improve performance of financial management as well as optimize financial strategies for firms in future operations.Comment: 14 pages, 4 figure

Plus-minus construction leads to perfect invisibility

Recent theoretical advances applied to metamaterials have opened new avenues to design a coating that hides objects from electromagnetic radiation and even the sight. Here, we propose a new design of cloaking devices that creates perfect invisibility in isotropic media. A combination of positive and negative refractive indices, called plus-minus construction, is essential to achieve perfect invisibility (i.e., no time delay and total absence of reflection). Contrary to the common understanding that between two isotropic materials having different refractive indices the electromagnetic reflection is unavoidable, our method shows that surprisingly the reflection phenomena can be completely eliminated. The invented method, different from the classical impedance matching, may also find electromagnetic applications outside of cloaking devices, wherever distortions are present arising from reflections.Comment: 24 pages, 10 figure