Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Colloidal Quantum Dots-Based Upconversion Devices
Colloidal quantum dots (CQD) have narrow emission linewidth and adjustable bandgap, so that CQD based infrared detectors can realize a widely tunable infrared spectral range. In addition, the luminescence spectrum of CQDs is extremely narrow, the color saturation and purity are high, and the optical stability is excellent, which can be obtained by solution procession. Therefore, CQDs-based LEDs (QLEDs) have excellent performances of a wide color gamut, long life, and low cost. For CQD baesd upconverters, except for the top electrode, the entire device can be prepared by solution method, which greatly simplifies the preparation of the device and make the upconverters are available for use in the fields of flexible devices.
  • 502
  • 31 Mar 2022
Topic Review
Complementarity
In physics, complementarity is a conceptual aspect of quantum mechanics that Niels Bohr regarded as an essential feature of the theory. The complementarity principle holds that objects have certain pairs of complementary properties which cannot all be observed or measured simultaneously. An example of such a pair is position and momentum. Bohr considered one of the foundational truths of quantum mechanics to be the fact that setting up an experiment to measure one quantity of a pair, for instance the position of an electron, excludes the possibility of measuring the other, yet understanding both experiments is necessary to characterize the object under study. In Bohr's view, the behavior of atomic and subatomic objects cannot be separated from the measuring instruments that create the context in which the measured objects behave. Consequently, there is no "single picture" that unifies the results obtained in these different experimental contexts, and only the "totality of the phenomena" together can provide a completely informative description.
  • 532
  • 14 Nov 2022
Topic Review
Conceptual Programs in Physics
Different subfields of physics have different programs for determining the state of a physical system.
  • 212
  • 18 Oct 2022
Topic Review
Dirac Equation in the Algebra of Physical Space
The Dirac equation, as the relativistic equation that describes spin 1/2 particles in quantum mechanics, can be written in terms of the Algebra of physical space (APS), which is a case of a Clifford algebra or geometric algebra that is based on the use of paravectors. The Dirac equation in APS, including the electromagnetic interaction, reads Another form of the Dirac equation in terms of the Space time algebra was given earlier by David Hestenes. In general, the Dirac equation in the formalism of geometric algebra has the advantage of providing a direct geometric interpretation.
  • 214
  • 17 Oct 2022
Biography
Edwin C. Kemble
Edwin Crawford Kemble (January 28, 1889 in Delaware, Ohio – March 12, 1984) was an American physicist who made contributions to the theory of quantum mechanics and molecular structure and spectroscopy. During World War II, he was a consultant to the Navy on acoustic detection of submarines and to the Army on Operation Alsos.[1] Kemble began college in 1906 at Ohio Wesleyan University, but h
  • 423
  • 08 Dec 2022
Topic Review
Englert–Greenberger–Yasin Duality Relation
The Englert–Greenberger–Yasin duality relation, often called the Englert–Greenberger relation, relates the visibility, [math]\displaystyle{ V }[/math], of interference fringes with the definiteness, or distinguishability, [math]\displaystyle{ D }[/math], of the photons' paths in quantum optics. As an inequality: Although it is treated as a single relation, it actually involves two separate relations, which mathematically look very similar. The first relationship was first experimentally shown by Greenberger and Yasin in 1988. It was later theoretically derived by Jaeger, Shimony, and Vaidman in 1995. This relation involves correctly guessing which of the two paths the particle would have taken, based on the initial preparation. Here [math]\displaystyle{ D }[/math] can be called the predictability, and is sometimes denoted by [math]\displaystyle{ P }[/math]. A year later Englert, in 1996, apparently unaware of this result, derived a related relation which dealt with knowledge of the two paths using an apparatus. Here [math]\displaystyle{ D }[/math] is called the distinguishability. The significance of the relation is that it expresses quantitatively the complementarity of wave and particle viewpoints in double slit experiments. The complementarity principle in quantum mechanics, formulated by Niels Bohr, says that the wave and particle aspects of quantum objects cannot be observed at the same time. The Englert–Greenberger relation makes this more precise; an experiment can yield partial information about the wave and particle aspects of a photon simultaneously, but the more information a particular experiment gives about one, the less it will give about the other. The distinguishability [math]\displaystyle{ D }[/math] which expresses the degree of probability with which path of the particle is known, is a measure of the particle information, while the visibility of the fringes [math]\displaystyle{ V }[/math] is a measure of the wave information. The relation shows that they are inversely related, as one goes up, the other goes down.
  • 329
  • 18 Oct 2022
Topic Review
Event Symmetry
In physics, event symmetry includes invariance principles that have been used in some discrete approaches to quantum gravity where the diffeomorphism invariance of general relativity can be extended to a covariance under every permutation of spacetime events.
  • 665
  • 07 Nov 2022
Topic Review
False Vacuum
In quantum field theory, a false vacuum is a hypothetical vacuum that is somewhat, but not entirely, stable. It may last for a very long time in that state, and might eventually move to a more stable state. The most common suggestion of how such a change might happen is called bubble nucleation – if a small region of the universe by chance reached a more stable vacuum, this "bubble" (also called "bounce") would spread. A false vacuum exists at a local minimum of energy and is therefore not stable, in contrast to a true vacuum, which exists at a global minimum and is stable. It may be very long-lived, or metastable.
  • 1.7K
  • 24 Oct 2022
Topic Review Peer Reviewed
Foundations of Quantum Mechanics
Quantum mechanics is a mathematical formalism that models the dynamics of physical objects. It deals with the elementary constituents of matter (atoms, subatomic and elementary particles) and of radiation. It is very accurate in predicting observable physical phenomena, but has many puzzling properties. The foundations of quantum mechanics are a domain in which physics and philosophy concur in attempting to find a fundamental physical theory that explains the puzzling features of quantum mechanics, while remaining consistent with its mathematical formalism. Several theories have been proposed for different interpretations of quantum mechanics. However, there is no consensus regarding any of these theories.
  • 1.8K
  • 07 Jun 2022
Topic Review
Fractional Schrödinger Equation
The fractional Schrödinger equation is a fundamental equation of fractional quantum mechanics. It was discovered by Nick Laskin (1999) as a result of extending the Feynman path integral, from the Brownian-like to Lévy-like quantum mechanical paths. The term fractional Schrödinger equation was coined by Nick Laskin.
  • 847
  • 24 Oct 2022
  • Page
  • of
  • 6
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
Feedback