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Topic Review
Libra
The constellation Libra, known as the Scales or the Balance, is one of the 12 zodiac constellations representing an inanimate object. It is located in the southern sky and is associated with justice and balance. Libra is depicted as scales held by the Greek goddess of justice, Astraea, and is the only zodiac constellation named after an object rather than an animal or character from mythology.
  • 630
  • 15 Mar 2024
Topic Review
Lieb-Robinson Bounds
The Lieb-Robinson bound is a theoretical upper limit on the speed at which information can propagate in non-relativistic quantum systems. It demonstrates that information cannot travel instantaneously in quantum theory, even when the relativity limits of the speed of light are ignored. The existence of such a finite speed was discovered mathematically by Elliott H. Lieb and Derek W. Robinson (de) in 1972. It turns the locality properties of physical systems into the existence of, and upper bound for this speed. The bound is now known as the Lieb-Robinson bound and the speed is known as the Lieb-Robinson velocity. This velocity is always finite but not universal, depending on the details of the system under consideration. For finite-range, e.g. nearest-neighbor, interactions, this velocity is a constant independent of the distance travelled. In long-range interacting systems, this velocity remains finite, but it can increase with the distance travelled. In the study of quantum systems such as quantum optics, quantum information theory, atomic physics, and condensed matter physics, it is important to know that there is a finite speed with which information can propagate. The theory of relativity shows that no information, or anything else for that matter, can travel faster than the speed of light. When non-relativistic mechanics is considered, however, (Newton's equations of motion or Schrödinger's equation of quantum mechanics) it had been thought that there is then no limitation to the speed of propagation of information. This is not so for certain kinds of quantum systems of atoms arranged in a lattice, often called quantum spin systems. This is important conceptually and practically, because it means that, for short periods of time, distant parts of a system act independently. One of the practical applications of Lieb-Robinson bounds is quantum computing. Current proposals to construct quantum computers built out of atomic-like units mostly rely on the existence of this finite speed of propagation to protect against too rapid dispersal of information. 
  • 422
  • 20 Oct 2022
Topic Review
LiFi Network
Light Fidelity (LiFi), a new technology that uses light to transmit data as a high-speed wireless connection system from a wide spectrum of domains.
  • 732
  • 01 Dec 2021
Topic Review
Lifshitz Theory of Van Der Waals Force
In condensed matter physics and physical chemistry, the Lifshitz theory of van der Waals forces, sometimes called the macroscopic theory of van der Waals forces, is a method proposed by Evgeny Mikhailovich Lifshitz in 1954 for treating van der Waals forces between bodies which does not assume pairwise additivity of the individual intermolecular forces; that is to say, the theory takes into account the influence of neighboring molecules on the interaction between every pair of molecules located in the two bodies, rather than treating each pair independently.
  • 1.6K
  • 03 Nov 2022
Topic Review
Light Curve Classification
Light curves are plots of brightness measured over time. In the field of Space Situational Awareness (SSA), light curves of Resident Space Objects (RSOs) can be utilized to infer information about an RSO such as the type of object, its attitude, and its shape.
  • 317
  • 18 Sep 2023
Topic Review
LIGO
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. These can detect a change in the 4 km mirror spacing of less than a ten-thousandth the charge diameter of a proton, equivalent to measuring the distance from Earth to Proxima Centauri (4.0208x1013km) with an accuracy smaller than the width of a human hair. The initial LIGO observatories were funded by the National Science Foundation (NSF) and were conceived, built, and are operated by Caltech and MIT. They collected data from 2002 to 2010 but no gravitational waves were detected. The Advanced LIGO Project to enhance the original LIGO detectors began in 2008 and continues to be supported by the NSF, with important contributions from the UK Science and Technology Facilities Council, the Max Planck Society of Germany, and the Australian Research Council. The improved detectors began operation in 2015. The detection of gravitational waves was reported in 2016 by the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration with the international participation of scientists from several universities and research institutions. Scientists involved in the project and the analysis of the data for gravitational-wave astronomy are organized by the LSC, which includes more than 1000 scientists worldwide, as well as 440,000 active Einstein@Home users (As of December 2016). LIGO is the largest and most ambitious project ever funded by the NSF. In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry C. Barish "for decisive contributions to the LIGO detector and the observation of gravitational waves." "The Nobel Prize in Physics 2017". Nobel Foundation. https://www.nobelprize.org/nobel_prizes/physics/laureates/2017/press.html.  As of March 2018, LIGO has made six detections of gravitational waves, of which the first five were colliding black-hole pairs. The sixth detected event, on August 17, 2017, was the first detection of a collision of two neutron stars, which simultaneously produced optical signals detectable by conventional telescopes.
  • 1.4K
  • 25 Oct 2022
Topic Review
Line-Shaped-Illumination Two-Photon Microscopy
Line-shaped illumination is a useful configuration to obtain a multifocal pattern to be used in two-photon microscopy: the light beam emitted by the illuminating laser is first shaped by means of cylindrical lenses and then is focused inside the sample as a continuous line. The simultaneous excitation of several points in the specimen is expected to reduce the acquisition time with respect to the usual point-scanning two-photon microscopes, as a two-dimensional image is obtained by scanning the line along a single direction.
  • 565
  • 05 May 2022
Topic Review
Lipid Bilayers on Silicon Substrates
Artificial membranes are models for biological systems that are important for several applications. In the present entry we talk about artificial membranes such as supported lipid bilayers (SLB) and ways to self- assemble them. We mainly focus on the results of a new dry evaporation process in high vacuum, i.e., physical vapor deposition, to make samples of dipalmitoylphosphatidylcholine (DPPC) on silicon substrates. We have characterized the main phase transitions and adhesion of our SLBs using high-resolution ellipsometry and AFM techniques. The finding of this new SLB fabrication approach is relevant for the understanding the interaction of lipid bilayers in contact with surfaces in dry environments, with the aim to develop new kinds of lab-on-chip bionanosensors. This discovery is especially relevant in the context of the viability of organisms covered with lipid bilayer structures. An example of this kind of interaction occurs between bilayer-protected viruses, e.g., corona viruses, and solid surfaces, allowing the virus to stay active during long periods of time. The prolonged stability of SLBs on dry SiO2/Si substrates detected in our research can explain the long-term stability of some viruses deposited or adsorbed on dry surfaces, including the SARS-CoV-2 virus. 
  • 1.0K
  • 03 Nov 2020
Topic Review
Liquid Crystal Aided Nanotechnology/Nanoscience
The research field of liquid crystals and their applications is recently changing from being largely focused on display applications and optical shutter elements in various fields, to quite novel and diverse applications in the area of nanotechnology and nanoscience. Functional nanoparticles, such as ferroelectric and magnetic particles, have recently been used to a significant extent to modify the physical properties of liquid crystals. Also, intriguing photonic functionalities can be realized by adding nanoparticles such as quantum dots, metal particles, semiconductors, etc. into liquid crystals. The self-organization of liquid crystal molecules is exploited to used as order templates to orient nanoparticles. Similarly, anisodiametric nanoparticles such as rods, nanotubes and flakes are shown to form lyotropic liquid crystal phases in the presence of isotropic host solvents at a certain concentration.
  • 2.2K
  • 27 Oct 2020
Topic Review
Liquid Crystal Lenses
Liquid crystal (LC) lenses may be used by themselves or as a supplement of glass lenses, e.g., to tune up the power of the glass lens within a certain range, with functionality equivalent to commercial progressive lenses, but with improved performance since the power of the whole lens is modified by a sensor providing autofocus, as in digital cameras.
  • 258
  • 29 Dec 2023
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