arXiv subjects

Chenguang Lu

Publications and source records attributed to Chenguang Lu.

23 records · Page 2Linked to original sources

arXiv2013

Tunable electronic correlation effects in nanotube-light interactions

Electronic many-body correlation effects in one-dimensional (1D) systems such as carbon nanotubes have been predicted to modify strongly the nature of photoexcited states. Here we directly probe this effect using broadband elastic light scattering from individual suspended carbon nanotubes under electrostatic gating conditions. We observe significant shifts in optical transition energies, as well as line broadening, as the carrier density is increased. The results demonstrate the differing role of screening of many-body electronic interactions on the macroscopic and microscopic length scales, a feature inherent to quasi-1D systems. Our findings further demonstrate the possibility of electrical tuning of optical transitions and provide a basis for understanding of various optical phenomena in carbon nanotubes and other quasi-1D systems in the presence of charge carrier doping.

cond-mat.mes-hall↗

arXiv2012

GPS Information and Rate Tolerance - Clarifying Relationship between Rate Distortion and Complexity Distortion

I proposed rate tolerance and discussed its relation to rate distortion in my book "A Generalized Information Theory" published in 1993. Recently, I examined the structure function and the complexity distortion based on Kolmogorov's complexity theory. It is my understanding now that complexity-distortion is only a special case of rate tolerance while constraint sets change from fuzzy sets into clear sets that look like balls with the same radius. It is not true that the complexity distortion is generally equivalent to rate distortion as claimed by the researchers of complexity theory. I conclude that a rate distortion function can only be equivalent to a rate tolerance function and both of them can be described by a generalized mutual information formula where P(Y|X) is equal to P(Y|Tolerance). The paper uses GPS as an example to derive generalized information formulae and proves the above conclusions using mathematical analyses and a coding example. The similarity between the formula for measuring GPS information and the formula for rate distortion function can deepen our understanding the generalized information measure.

cs.IT↗

arXiv2010

Illustrating Color Evolution and Color Blindness by the Decoding Model of Color Vision

A symmetrical model of color vision, the decoding model as a new version of zone model, was introduced. The model adopts new continuous-valued logic and works in a way very similar to the way a 3-8 decoder in a numerical circuit works. By the decoding model, Young and Helmholtz's tri-pigment theory and Hering's opponent theory are unified more naturally; opponent process, color evolution, and color blindness are illustrated more concisely. According to the decoding model, we can obtain a transform from RGB system to HSV system, which is formally identical to the popular transform for computer graphics provided by Smith (1978). Advantages, problems, and physiological tests of the decoding model are also discussed.

cs.CV↗

arXiv2007

A Generalized Information Formula as the Bridge between Shannon and Popper

A generalized information formula related to logical probability and fuzzy set is deduced from the classical information formula. The new information measure accords with to Popper's criterion for knowledge evolution very much. In comparison with square error criterion, the information criterion does not only reflect error of a proposition, but also reflects the particularity of the event described by the proposition. It gives a proposition with less logical probability higher evaluation. The paper introduces how to select a prediction or sentence from many for forecasts and language translations according to the generalized information criterion. It also introduces the rate fidelity theory, which comes from the improvement of the rate distortion theory in the classical information theory by replacing distortion (i.e. average error) criterion with the generalized mutual information criterion, for data compression and communication efficiency. Some interesting conclusions are obtained from the rate-fidelity function in relation to image communication. It also discusses how to improve Popper's theory.

cs.IT↗

arXiv2007

Subjective Information Measure and Rate Fidelity Theory

Using fish-covering model, this paper intuitively explains how to extend Hartley's information formula to the generalized information formula step by step for measuring subjective information: metrical information (such as conveyed by thermometers), sensory information (such as conveyed by color vision), and semantic information (such as conveyed by weather forecasts). The pivotal step is to differentiate condition probability and logical condition probability of a message. The paper illustrates the rationality of the formula, discusses the coherence of the generalized information formula and Popper's knowledge evolution theory. For optimizing data compression, the paper discusses rate-of-limiting-errors and its similarity to complexity-distortion based on Kolmogorov's complexity theory, and improves the rate-distortion theory into the rate-fidelity theory by replacing Shannon's distortion with subjective mutual information. It is proved that both the rate-distortion function and the rate-fidelity function are equivalent to a rate-of-limiting-errors function with a group of fuzzy sets as limiting condition, and can be expressed by a formula of generalized mutual information for lossy coding, or by a formula of generalized entropy for lossless coding. By analyzing the rate-fidelity function related to visual discrimination and digitized bits of pixels of images, the paper concludes that subjective information is less than or equal to objective (Shannon's) information; there is an optimal matching point at which two kinds of information are equal; the matching information increases with visual discrimination (defined by confusing probability) rising; for given visual discrimination, too high resolution of images or too much objective information is wasteful.

cs.IT↗