Chaos in one-dimensional lattices under intense laser fields

A model is investigated where a monochromatic, spatially homogeneous laser field interacts with an electron in a one-dimensional periodic lattice. The classical Hamiltonian is presented and the technique of stroboscopic maps is used to study the dynamical behavior of the model. The electron motion is found to be completely regular only for small field amplitudes, developing a larger chaotic region as the amplitude increases. The quantum counterpart of the classical Hamiltonian is derived. Exact numerical diagonalizations show the existence of universal, random-matrix fluctuations in the electronic energy bands dressed by the laser field. A detailed analysis of the classical phase space is compatible with the statistical spectral analysis of the quantum model. The application of this model to describe transport and optical absorption in semiconductor superlattices submitted to intense infrared laser radiation is proposed.Comment: 9 pages, RevTex 3.0, EPSF (6 figures), to appear in Europhys. J.

Semiclassical Tunneling of Wavepackets with Real Trajectories

Semiclassical approximations for tunneling processes usually involve complex trajectories or complex times. In this paper we use a previously derived approximation involving only real trajectories propagating in real time to describe the scattering of a Gaussian wavepacket by a finite square potential barrier. We show that the approximation describes both tunneling and interferences very accurately in the limit of small Plank's constant. We use these results to estimate the tunneling time of the wavepacket and find that, for high energies, the barrier slows down the wavepacket but that it speeds it up at energies comparable to the barrier height.Comment: 23 pages, 7 figures Revised text and figure

Quantum Key Distribution using Continuous-variable non-Gaussian States

In this work we present a quantum key distribution protocol using continuous-variable non-Gaussian states, homodyne detection and post-selection. The employed signal states are the Photon Added then Subtracted Coherent States (PASCS) in which one photon is added and subsequently one photon is subtracted. We analyze the performance of our protocol, compared to a coherent state based protocol, for two different attacks that could be carried out by the eavesdropper (Eve). We calculate the secret key rate transmission in a lossy line for a superior channel (beam-splitter) attack, and we show that we may increase the secret key generation rate by using the non-Gaussian PASCS rather than coherent states. We also consider the simultaneous quadrature measurement (intercept-resend) attack and we show that the efficiency of Eve's attack is substantially reduced if PASCS are used as signal states.Comment: We have included an analysis of the simultaneous quadrature measurement attack plus 2 figures; we have also clarified some point

Using the Sound Card as a Timer

Experiments in mechanics can often be timed by the sounds they produce. In such cases, digital audio recordings provide a simple way of measuring time intervals with an accuracy comparable to that of photogate timers. We illustrate this with an experiment in the physics of sports: to measure the speed of a hard-kicked soccer ball.Comment: 3 pages, 4 figures, Late

Do memes impact brand coolness perceptions? Examining hedonic versus utilitarian products

Digital platforms are one of the best tools to connect consumers worldwide (Nieubuur, 2021). Specifically, in the first quarter of 2021, Facebook alone had an active user base of 2.91 billion users, YouTube had 2.29 billion active users, while Instagram had 1.39 billion active users (Statista, 2021). Following Chuah et al. (2020), content is key in the digital environment. With such high numbers of online users, and the need for keeping them interested, memes became a frequently used content to interact with consumers. Internet Memes (IMs) usually take the form of animations, GIFs, videos, images, and image macros. As IMs are flexible, and able to relate to many expressions (e.g., humour, advice, irony, sarcasm), brands can easily integrate IMs in their strategy. Besides establishing a connection between brands and consumers worldwide, social media also allows users to check the latest trends, and most importantly, what is cool nowadays. Coolness reflects consumers’ perceptions of a brand or product’s quality, distinctiveness, or novelty (Sundar et al., 2014). Thus, being a cool brand and having cool content is becoming increasingly important to managers and practitioners. IMs are easy to understand, fun, “shareable” and can have a positive impact on consumer behaviour (Nieubuur, 2021). Brand Coolness (BC) also shows to have a positive impact on the consumer decision-making process (Warren et al., 2019). However, there is a gap in the literature concerning the relationship between IMs and BC perceptions. Although there is a variety of studies concerning BC effects on consumer decision making, to our knowledge, there is no literature establishing a connection between IMs and BC. Thus, the present study aims to understand if IMs influence consumers’ BC perceptions, in the context of hedonic versus utilitarian personal beauty items. A survey was conducted, to assess the impact of utilitarian (Colgate) and hedonic (Dior) brands through IMs. A multiple linear regression was performed to predict brand coolness perceptions on hedonic versus utilitarian brands, with and without the meme. Our findings suggest that, when not using a meme, the utilitarian brand (Colgate), is associated with the energetic and authentic characteristics. On another hand, when the brand uses the meme, the brand coolness perceptions are explained by the useful/extraordinary and original dimensions. As for the hedonic brand, when not using the IM, the brand (Dior) is associated with energetic, authentic, and iconic brand coolness dimensions. However, when using the IM, the hedonic brand is associated with useful/extraordinary, energetic, popular, and subcultural dimensions. Our results are in accordance with the brand coolness and internet memes’ literature: (1) brands do not need to be associated with the ten coolness characteristics, since the perception of BC differs from brand to brand, and across consumers (Warren et al., 2019); (2) IMs have specific characteristics (such as iconicity, humour, popularity, (Chuah et al., 2020), it was expected that introducing them would change consumers perceptions. We also acknowledge the importance of the results to academics and practitioners. To our knowledge, this is the first attempt to analyse specific dimensions of brand coolness in the context of hedonic versus utilitarian products as reflected by IMs, contributing to the marketing and branding literature. As for managers, brands can use digital marketing channels to enhance popularity through IMs. As IMs can take many forms and is easily adapted, the tool is a cool way of advertising our products. Plus, it is easy to share between consumers, which increases chances of becoming viral through social media.info:eu-repo/semantics/acceptedVersio

Geometric combinatorial algebras: cyclohedron and simplex

In this paper we report on results of our investigation into the algebraic structure supported by the combinatorial geometry of the cyclohedron. Our new graded algebra structures lie between two well known Hopf algebras: the Malvenuto-Reutenauer algebra of permutations and the Loday-Ronco algebra of binary trees. Connecting algebra maps arise from a new generalization of the Tonks projection from the permutohedron to the associahedron, which we discover via the viewpoint of the graph associahedra of Carr and Devadoss. At the same time that viewpoint allows exciting geometrical insights into the multiplicative structure of the algebras involved. Extending the Tonks projection also reveals a new graded algebra structure on the simplices. Finally this latter is extended to a new graded Hopf algebra (one-sided) with basis all the faces of the simplices.Comment: 23 figures, new expanded section about Hopf algebra of simplices, with journal correction