11 research outputs found
Energy transport faster than light in good conductors and superconductors
People need a model to study tachyons whose prediction can be tested easily.
The dispersion relation w^2=k^2C^2-a^2C^2 of a low-frequency electromagnetic
field in good conductors is equivalent to the energy-momentum equation
E^2=p^2C^2-m^2C^4 of a tachyon where the proportionality coefficient is h^2. An
experiment in 1980s to measure the phase velocity Vp [1] can be regarded as an
indirect evidence of the superluminal velocity V>>c of those photons just
equals the rate of energy flow S/w of the field.Instability of the tachyonic
field corresponds to the Joule heat. To detect the speed of energy is difficult
and we plan to modulate signals to observe the information velocity (speed of
points of non-analyticity)[2].Comment: 16 page
Propagation of light through small clouds of cold interacting atoms
We demonstrate experimentally that a cloud of cold atoms with a size
comparable to the wavelength of light can induce large group delays on a laser
pulse when the laser is tightly focused on it and is close to an atomic
resonance. Delays as large as -10 ns are observed, corresponding to
"superluminal" propagation with negative group velocities as low as -300 m/s.
Strikingly, this large delay is associated with a moderate extinction owing to
the very small size of the cloud and to the light-induced interactions between
atoms. It implies that a large phase shift is imprinted on the continuous laser
beam, and opens interesting perspectives for applications to quantum
technologies.Comment: 5 pages, 3 figures Supplemental Material : 2 pages, 2 Figure
Superluminal propagation from IR physics
One may believe that front velocities of waves in a given theory coincide
with the UV limit of phase velocities for any dispersion relations. This
implies that IR physics is irrelevant to the discussion of propagation speed of
waves. We first consider a theory that contains higher spatial derivatives in
the wave equation and prove that front velocities coincide with the UV limit of
phase velocities, at least, if parity is conserved. However, we also show that
front velocities do not coincide with the UV limit of phase velocities in
general dispersion relations. We explicitly give several examples in which
front velocities are superluminal owing to an IR or intermediate energy scale
property of dispersion relations even if the UV limit of phase velocities is
luminal. Our finding conveys the important caution that not only UV physics but
also IR physics can be significant to superluminality.Comment: 10 pages, 4 figure
Causality and the AdS Dirichlet problem
The (planar) AdS Dirichlet problem has previously been shown to exhibit
superluminal hydrodynamic sound modes. This problem is defined by bulk
gravitational dynamics with Dirichlet boundary conditions imposed on a rigid
timelike cut-off surface. We undertake a careful examination of this set-up and
argue that, in most cases, the propagation of information between points on the
Dirichlet hypersurface is nevertheless causal with respect to the induced light
cones. In particular, the high-frequency dynamics is causal in this sense.
There are however two exceptions and both involve boundary gravitons whose
propagation is not constrained by the Einstein equations. These occur in i)
AdS, where the boundary gravitons generally do not respect the induced
light cones on the boundary, and ii) Rindler space, where they are related to
the infinite speed of sound in incompressible fluids. We discuss implications
for the fluid/gravity correspondence with rigid Dirichlet boundaries and for
the black hole membrane paradigm.Comment: 29 pages, 5 figures. v2: added refs. v3: minor clarification
Tachyons and other Things fast: A study of superluminal motion
This project examines two different types of superluminal motions. The first is of a theoretical particle known as the tachyon, whose existence is not forbidden by the laws of physics but which has never been observed. An interpretation of the interactions of tachyons with ordinary (subluminal) particles is given and a paradox involving tachyons is discussed. The second type of superluminal motion studied is connected with faraway galaxies. However the faster than light motion observed here is only apparent and can be understood on the basis of the known laws of physics. Data related to this effect is presented and analyzed
Advanced radiating systems based on leaky wave and nondiffracting waves
In recent years, microwave, millimeter-wave, and THz applications such as medical and security imaging, wireless power transfer, and near-field focusing, just to mention but a few, have gained much attention in the area of ICT due to their potentially high social impact. On one hand, the need of highly-directive THz sensors with tunable radiating features in the far-field region has recently boosted the research activity in the design of flexible, low-cost and low-profile devices. On the other hand, it is of paramount importance to focus energy in the near-field region, and thus the generation of limited-diffraction waves in the microwave and millimeter-wave regime is a topic of recent increasing interest. In this context, leaky-wave theory is an elegant and extremely useful formalism which allows for describing in a common fashion guiding and radiating phenomena in both the near field and the far field, spanning frequencies from microwaves to optics passing through THz. In this PhD thesis we aim to exploit the intrinsic versatility of the leakywave approach to design advanced radiating systems for controlling the far-field radiating features at THz frequencies and for focusing electromagnetic radiation in the near field at millimeter waves. Specifically, the use of relatively new materials such as graphene and liquid crystals has been considered for the design of leaky-wave based radiators, achieving very promising results in terms of reconfigurability, efficiency, and radiating capabilities. In this context, an original theoretical analysis has provided new general formulas for the evaluation of the radiating features (e.g., half-power beamwidth, sidelobe level, etc.) of leaky-wave antennas. Indeed, the current formulations are based on several simplifying hypotheses which do not allow for an accurate evaluation of the beamwidth in different situations. In addition to the intriguing reconfigurable capabilities offered by leaky waves in far-field applications, interesting focusing capabilities can be obtained in the near field. In particular, it is shown that leaky waves can profitably be used to generate limited-diffraction Bessel beams by means of narrow-band radiators in the microwave range. Also, the use of higher-order leaky-wave modes allows for achieving almost the same performance in the millimeter-wave range, where previous designs were subjected to severe fabrication issues. Even more interestingly, the limited-diffractive character of Bessel beams can also be used to generate limited-diffraction pulses as superpositions of monochromatic Bessel beams over a considerable fractional bandwidth. In this context, a novel theoretical framework has been developed to understand the practical limitations to efficiently generate limited-diffraction, limited-dispersion pulses, such as X-waves, in the microwave/millimeter-wave range. As a result of this investigation, a class of wideband radiators has been thoroughly analyzed, showing promising capabilities for the generation of both zeroth-order and higher-order Xwaves. The latter may pave the way for the first localized transmission of orbital angular momentum in the microwave range
Two deductions: (1) from the totality to quantum information conservation; (2) from the latter to dark matter and dark energy
The paper discusses the origin of dark matter and dark energy from the concepts of time and the totality in the final analysis. Though both seem to be rather philosophical, nonetheless they are postulated axiomatically and interpreted physically, and the corresponding philosophical transcendentalism serves heuristically. The exposition of the article means to outline the âforest for the treesâ, however, in an absolutely rigorous mathematical way, which to be explicated in detail in a future paper. The âtwo deductionsâ are two successive stage of a single conclusion mentioned above. The concept of âtranscendental invarianceâ meaning ontologically and physically interpreting the mathematical equivalence of the axiom of choice and the well-ordering âtheoremâ is utilized again. Then, time arrow is a corollary from that transcendental invariance, and in turn, it implies quantum information conservation as the Noether correlate of the linear âincrease of timeâ after time arrow. Quantum information conservation implies a few fundamental corollaries such as the âconservation of energy conservationâ in quantum mechanics from reasons quite different from those in classical mechanics and physics as well as the âabsence of hidden variablesâ (versus Einsteinâs conjecture) in it. However, the paper is concentrated only into the inference of another corollary from quantum information conservation, namely, dark matter and dark energy being due to entanglement, and thus and in the final analysis, to the conservation of quantum information, however observed experimentally only on the âcognitive screenâ of âMachâs principleâ in Einsteinâs general relativity. therefore excluding any other source of gravitational field than mass and gravity. Then, if quantum information by itself would generate a certain nonzero gravitational field, it will be depicted on the same screen as certain masses and energies distributed in space-time, and most presumably, observable as those dark energy and dark matter predominating in the universe as about 96% of its energy and matter quite unexpectedly for physics and the scientific worldview nowadays. Besides on the cognitive screen of general relativity, entanglement is available necessarily on still one âcognitive screenâ (namely, that of quantum mechanics), being furthermore âflatâ. Most probably, that projection is confinement, a mysterious and ad hoc added interaction along with the fundamental tree ones of the Standard model being even inconsistent to them conceptually, as far as it need differ the local space from the global space being definable only as a relation between them (similar to entanglement). So, entanglement is able to link the gravity of general relativity to the confinement of the Standard model as its projections of the âcognitive screensâ of those two fundamental physical theories
The Chinese continuum of self-cultivation: a Confucian-Deweyan learning model
This thesis explores a transcultural philosophy of education based on the Neo-Confucian concepts of the universal nature of self (ren xingäșșæ§), as positioned with self-in-the-world (ren äșș) and humanity (ren ä») in the co-creative process of self-cultivation (xiushen äżźèș«). This approach to knowledge synthesis and consolidation informs and enhances the educational theories of John Dewey (1859-1952) and presents a philosophy of education which has a dynamic self interacting with and becoming in the world as an evolving process of knowledge schematization and application. The Confucian-Deweyan educational model explored herein is presented as, not only a transcultural educational approach in the changing face of globality, but also a means to encourage and foster humanitarian and communitarian values in the student to be applied in life-long learning. That is, a wholistic approach to education whereby the individual considers the other â human and natural â tantamount to the self in an increasingly shifting world. This concept is in direct opposition to the anthropocentric approach of egoistic individualism currently prevalent in post-modern societies. Hence, the model developed herein is a pragmatic response to 21st century globality, fostering cooperation, rather than competition; an anthropocosmic vision of life and living, enabling non-European indigenous values to co-exist in a global arena. The specific elements addressed for the contextual background of the thesis is the history and influence of Deweyan thought in China (Dewey lectured in China for two years â 1919-1921), the history of Chinaâs educational systems, and the PRCâs current education reform initiatives. China, with a community-based culture and growing global presence, offers a real-world context for exploring the viability of such a Confucian-Deweyan model of education as a confluence of Western and Eastern approaches to learning, self, community, creativity and knowledge