Filters

Results

**1**-**10**of**177** Results

**1**-**10**of**177**. Search took:**0.021**secondsSort by: date | relevance |

AbstractAbstract

[en] It is suggested that the structure of space-time can be studied from the invariance of c and h with cosmic time

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] By considering the allowed values of the z-component of the quantum mechanical angular momentum operator, a simple explanation is given for the term l(l+1)

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] It is shown that the electric field lines of a electric dipole droop and thus the dipole receives an upward force balancing that of gravity

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] It is pointed out that the formula for the upward acceleration of a submerged, buoyant sphere should contain the effective mass of the water that is accelerated downward

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] The availability of powerful microcomputers with graphics capabilities expands the range of numerical procedures that can be employed for undergraduate use. The use of simple software packages for the evaluation of multidimensional WKB approximate eigenvalues is discussed. Introductory courses in quantum mechanics rarely make use of semiclassical theories, such as WKB, to relate quantum mechanics to classical mechanics. This relationship can be helpful for the student's understanding of quantum mechanics, and a computer experiment can provide a useful avenue for making the concepts concrete. The major components of the approach involve the use of a package for the integration of differential equations, to treat the classical equations of motion, and a computer-aided design package to determine the phase integral areas. The codes are not expensive, and all exploit the graphical capabilities of microcomputers, which are critical for visualizing the relationship between classical and quantum ideas

Primary Subject

Secondary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] We give some illustrations and interpretations of supersymmetry in quantum mechanics in simple models. We show that the value of 2 for the g factor of the electron expresses the presence of supersymmetry in the Hamiltonian for an electron in a uniform magnetic field. The problem is considered both in the Schroedinger and Dirac formulations. We also show that the radial Coulomb problem with orbital angular momentum l, nuclear charge Z, and principal quantum number n, is supersymmetrically linked to the similar problem with charge Z(1-1/n) and quantum number n-1. Thereby the dependence of Coulomb energies only on the combination Z/n is seen as a manifestation of the supersymmetry in the radial Coulomb problem. Other examples of supersymmetry we consider are the Morse potential, the three-dimensional isotropic oscillator, the states of the helium atom and those of the hydrogen atom in an extremely strong magnetic field

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] A unified description is presented for internal space-time symmetries of photons and neutrinos. Lorentz-boosted Dirac equation for a massive spin-1/2 particle is discussed in the Weyl representation. In the large-momentum/small-mass limit, the resulting large component of the Dirac spinor becomes invariant under transformations of the E(2)-like little group, and the small component is not invariant under the E(2)-like transformation. The gauge dependence of the photon four-potential can thus be derived from a direct product of the gauge-independent large component and the gauge-dependent small component

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] The authors discuss an alternative method of performing coupling constant perturbation expansions in nonrelativistic quantum mechanics. This method, called logarithmic perturbation theory, yields new expressions for any-order corrections E/sub n/ to an unperturbed bound-state energy which do not involve cumbersome sums over intermediate unperturbed states. In one dimension, these corrections E/sub n/ can be evaluated using a simple explicit form containing a small number of integrals. In more than one dimension the approach is systematic but computations require the solution of well-defined partial differential equations. For order n = 2 this equation is identical to that appearing in the method of Dalgarno and Lewis. Numerous illustrative examples are presented. 5 references

Primary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] To dispel a widespread but erroneous belief among physicists that the penetration of ac magnetic fields into normal metals is determined by the usual skin depth δ alone, a simple analysis is presented of two problems in each of which a different length scale determines the effective screening. For a cylindrical can of thickness d<<δ and radius R<<λ, where λ is the wavelength, it is shown that the critical thickness for effective screening is d/sub c/ = δ

^{2}/R. For a planar film with thickness d<<δ, d/sub c/ = c/2πσ, where σ is the conductivity. An exact analysis is also presented of the screening for a cylinder of arbitrary thickness, as well as an analogy between screening by normal metals and screening by superconductorsSecondary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] Rapid interstellar travel by means of spacetime wormholes is described in a way that is useful for teaching elementary general relativity. The description touches base with Carl Sagan's novel Contact, which, unlike most science fiction novels, treats such travel in a manner that accords with the best 1986 knowledge of the laws of physics. Many objections are given against the use of black holes or Schwarzschild wormholes for rapid interstellar travel. A new class of solutions of the Einstein field equations is presented, which describe wormholes that, in principle, could be traversed by human beings. It is essential in these solutions that the wormhole possess a throat at which there is no horizon; and this property, together with the Einstein field equations, places an extreme constraint on the material that generates the wormhole's spacetime curvature: In the wormhole's throat that material must possess a radial tension tau

_{0}with the enormous magnitude tau_{0}∼ (pressure at the center of the most massive of neutron stars) x (20 km)^{2}/(circumference of throat)^{2}. Moreover, this tension must exceed the material's density of mass-energy, rho_{0}c^{2}. No known material has this tau_{0}>rho_{0}c^{2}property, and such material would violate all the ''energy conditions'' that underlie some deeply cherished theorems in general relativity. However, it is not possible today to rule out firmly the existence of such material; and quantum field theory gives tantalizing hints that such material might, in fact, be possiblePrimary Subject

Record Type

Journal Article

Journal

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

1 | 2 | 3 | Next |