Regularized Casimir energy for an infinite dielectric cylinder subject to light-velocity conservation

The Casimir energy of a dilute dielectric cylinder, with the same light-velocity as in its surrounding medium, is evaluated exactly to first order in $\xi^2$ and numerically to higher orders in $\xi^2$. The first part is carried out using addition formulas for Bessel functions, and no Debye expansions are required

The Casimir Effect for Fermions in One Dimension

We study the Casimir problem for a fermion coupled to a static background field in one space dimension. We examine the relationship between interactions and boundary conditions for the Dirac field. In the limit that the background becomes concentrated at a point (a ``Dirac spike'') and couples strongly, it implements a confining boundary condition. We compute the Casimir energy for a masslike background and show that it is finite for a stepwise continuous background field. However the total Casimir energy diverges for the Dirac spike. The divergence cannot be removed by standard renormalization methods. We compute the Casimir energy density of configurations where the background field consists of one or two sharp spikes and show that the energy density is finite except at the spikes. Finally we define and compute an interaction energy density and the force between two Dirac spikes as a function of the strength and separation of the spikes.Comment: 18 pages, 6 figure

Calculation of Ground State Energy for Confined Fermion Fields

A method for renormalization of the Casimir energy of confined fermion fields in (1+1)D is proposed. It is based on the extraction of singularities which appear as poles at the point of physical value of the regularization parameter, and subsequent compensation of them by means of redefinition of the "bare" constants. A finite ground state energy of the two-phase hybrid model of fermion bag with chiral boson-fermion interaction is calculated as the function of the bag's size.Comment: 10 pages, LaTeX; no figures. Version to appear in Phys. Lett. B (2001

Twenty-first semiannual report to Congress, 1 January - 30 June 1969

Manned space flights, satellite observations, space sciences, and air traffic control - NASA report to Congress for 1 Jan. to 30 June 196

Toynbee\u27s Idea of Etherialization as a Criterion of Progress

Few ideals characterize the spirit of the West as does the ideal of progress. Indeed, so closely allied to the rise of the West has been the ideal of progress that doubts about it cast a shadow on the destiny of the West itself. These doubts have arisen. No longer does belief in progress command the prestige it once enjoyed. The assurance that civilization has moved, is moving, and will continue to move in a desirable direction is essentially bankrupt. In the eyes of the British historian, Arnold J. Toynbee, it is a fallaciously comfortable doctrine, a facile belief that Western Society could see ahead of it an unbroken vista of progress toward an Earthly Paradise. One need only note the sober observation of the American sociologist Edward A. Ross who wrote at the end of World War II that, the rosy doctrine in great favor a generation ago that man\u27s social progress is inevitable because brought about by impersonal forces working in his interest, will go into discard

Thermal Cracking Of Concrete Pile Caps

The large pile caps of buildings and bridges may have superficial cracks already in the early hours after concreting. Due to the large volume of concrete, the temperature inside the pile cap may reach very high values, as a result of the heat of hydration of cement. Because of the strong temperature gradients, the surface of the pile cap is tensioned and may crack. The employment of skin reinforcement does not avoid the cracking of concrete. However, this reinforcement may reduce the crack width, providing the onset of a large number of small cracks, instead of a single crack with large opening. The object of this work is to address this issue by analyzing the main variables involved and suggest a design methodology for the calculation of skin reinforcement of concrete pile caps