3 research outputs found
Minimum spanning trees on random networks
We show that the geometry of minimum spanning trees (MST) on random graphs is
universal. Due to this geometric universality, we are able to characterise the
energy of MST using a scaling distribution () found using uniform
disorder. We show that the MST energy for other disorder distributions is
simply related to . We discuss the relationship to invasion
percolation (IP), to the directed polymer in a random media (DPRM) and the
implications for the broader issue of universality in disordered systems.Comment: 4 pages, 3 figure
Similarity of slow stripe fluctations between Sr-doped cuprates and oxygen-doped nickelates
Stripe fluctuations in La2NiO4.17 have been studied by 139La NMR using the
field and temperature dependence of the linewidth and relaxation rates. In the
formation process of the stripes the NMR line intensity is maximal below 230K,
starts to diminish around 140K, disappears around 50K and recovers at 4K. These
results are shown to be consistent with, but completely complementary to
neutron measurements, and to be generic for oxygen doped nickelates and
underdoped cuprates.Comment: 4 pages including 4 figure
Instantaneous Spin Correlations in La2CuO4
We have carried out a neutron scattering study of the instantaneous spin-spin
correlations in La2CuO4 (T_N = 325 K) over the temperature range 337 K to 824
K. Incident neutron energies varying from 14.7 meV to 115 meV have been
employed in order to guarantee that the energy integration is carried out
properly. The results so-obtained for the spin correlation length as a function
of temperature when expressed in reduced units agree quantitatively both with
previous results for the two dimensional (2D) tetragonal material Sr2CuO2Cl2
and with quantum Monte Carlo results for the nearest neighbor square lattice
S=1/2 Heisenberg model. All of the experimental and numerical results for the
correlation length are well described without any adjustable parameters by the
behavior predicted for the quantum non-linear sigma model in the low
temperature renormalized classical regime. The amplitude, on the other hand,
deviates subtly from the predicted low temperature behavior. These results are
discussed in the context of recent theory for the 2D quantum Heisenberg model.Comment: 9 pages, LaTeX, includes 8 figure