1,233 research outputs found
Kaluza-Klein Vortices
We study static vortex type solutions of pure gravity for .
Non-singular vortex solutions can be obtained by considering periodic
Kaluza-Klein monopoles. We also show that away from the center of the vortices
the space is described by the gravitational instantons derived from minimal
surfaces.Comment: 9 pages, typos corrected, to appear in JHE
Phase Transition in Compact QED(3) and the Josephson Junction
We study the finite temperature phase transition in 2+1 dimensional compact
QED and its dual theory: Josephson junction. Duality of these theories at zero
temperature was established long time ago by Hosotani. Phase transition in
compact QED is well studied and we employ the `duality' to study the
superconductivity phase transition in a Josephson junction. For a thick
junction we obtain a critical temperature in terms of the geometrical
properties of the junction.Comment: 9 pages, discussion added about the role of the solitons. To appear
in JHE
Problems With Complex Actions
We consider Euclidean functional integrals involving actions which are not
exclusively real. This situation arises, for example, when there are -odd
terms in the the Minkowski action. Writing the action in terms of only real
fields (which is always possible), such terms appear as explicitly imaginary
terms in the Euclidean action. The usual quanization procedure which involves
finding the critical points of the action and then quantizing the spectrum of
fluctuations about these critical points fails. In the case of complex actions,
there do not exist, in general, any critical points of the action on the space
of real fields, the critical points are in general complex. The proper
definition of the function integral then requires the analytic continuation of
the functional integration into the space of complex fields so as to pass
through the complex critical points according to the method of steepest
descent. We show a simple example where this procedure can be carried out
explicitly. The procedure of finding the critical points of the real part of
the action and quantizing the corresponding fluctuations, treating the
(exponential of the) complex part of the action as a bounded integrable
function is shown to fail in our explicit example, at least perturbatively.Comment: 6+epsilon pages, no figures, presented at Theory CANADA
Two-element antenna-active phase shifter packaging at 77 GHz
This work presents a low cost and wire-bonded active phase shifter chip to RF circuitry on PCB board packaging for implementing a two-element phased array antenna at 77 GHz. The 1.5 mm and times; 1.1 mm chip is embedded in RO3003 PCB board and its GSG ports are wire-bonded to CPW lines that are expanded to feed the patch antenna on the PCB board. A low loss CPW to microstrip line transition is designed to exploit and transmit the signal from the GSG pads on the chip to the microstrip line on the PCB. The beam of the two-element array can be steered between and plusmn;20 and deg; by controlling the DC bias voltage of the active phase shifter chip
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