7,029 research outputs found
The energy density of an Ising half plane lattice
We compute the energy density at arbitrary temperature of the half plane
Ising lattice with a boundary magnetic field at a distance rows from
the boundary and compare limiting cases of the exact expression with recent
calculations at done by means of discrete complex analysis methods.Comment: 12 pages, 1 figur
Weber-like interactions and energy conservation
Velocity dependent forces varying as (such as Weber force), here called Weber-like forces, are examined
from the point of view of energy conservation and it is proved that they are
conservative if and only if . As a consequence, it is shown that
gravitational theories employing Weber-like forces cannot be conservative and
also yield both the precession of the perihelion of Mercury as well as the
gravitational deflection of light.Comment: latex, 11 pages, no figure
Monthly and Diurnal Variability of Rain Rate and Rain Attenuation during the Monsoon Period in Malaysia
Rain is the major source of attenuation for microwave propagation above 10 GHz. In tropical and equatorial regions where the rain intensity is higher, designing a terrestrial and earth-to-satellite microwave links is very critical and challenging at these frequencies. This paper presents the preliminary results of rain effects in a 23 GHz terrestrial point-to-point communication link 1.3km long. The experimental test bed had been set up at Skudai, Johor Bahru, Malaysia. In this area, a monsoon equatorial climate prevails and the rainfall rate can reach values well above 100mm/h with significant monthly and diurnal variability. Hence, it is necessary to implement a mitigation technique for maintaining an adequate radio link performance for the action of very heavy rain. Since we now know that the ULPC (Up Link Power Control) cannot guarantee the desired performance, a solution based on frequency band diversity is proposed in this paper. Here, a secondary radio link operating in a frequency not affected by rain (C band for instance) is placed parallel with the main link. Under no rain or light rain conditions, the secondary link carries without priority radio signals. When there is an outage of the main link due to rain, the secondary link assumes the priority traffic. The outcome of the research shows a solution for higher operating frequencies during rainy events
Hard hexagon partition function for complex fugacity
We study the analyticity of the partition function of the hard hexagon model
in the complex fugacity plane by computing zeros and transfer matrix
eigenvalues for large finite size systems. We find that the partition function
per site computed by Baxter in the thermodynamic limit for positive real values
of the fugacity is not sufficient to describe the analyticity in the full
complex fugacity plane. We also obtain a new algebraic equation for the low
density partition function per site.Comment: 49 pages, IoP styles files, lots of figures (png mostly) so using
PDFLaTeX. Some minor changes added to version 2 in response to referee
report
Integrability vs non-integrability: Hard hexagons and hard squares compared
In this paper we compare the integrable hard hexagon model with the
non-integrable hard squares model by means of partition function roots and
transfer matrix eigenvalues. We consider partition functions for toroidal,
cylindrical, and free-free boundary conditions up to sizes and
transfer matrices up to 30 sites. For all boundary conditions the hard squares
roots are seen to lie in a bounded area of the complex fugacity plane along
with the universal hard core line segment on the negative real fugacity axis.
The density of roots on this line segment matches the derivative of the phase
difference between the eigenvalues of largest (and equal) moduli and exhibits
much greater structure than the corresponding density of hard hexagons. We also
study the special point of hard squares where all eigenvalues have unit
modulus, and we give several conjectures for the value at of the
partition functions.Comment: 46 page
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