We investigate the three-dimensional O(2) model near the critical point by Monte Carlo simulations and calculate the major universal amplitude ratios of the model. The ratio U0 = A /A is determined directly from the specific heat data at zero magnetic field. The data do not, however, allow to extract an accurate estimate for α. Instead, we establish a strong correlation of U0 with the value of ...

We simulate lattice models in the three-dimensional XY universality class in the low and the high temperature phase. This allows us to compute a number of universal amplitude ratios with unprecedented precision: RΥ = 0.411(2), RB = 2.83(1), R + ξ = 0.3562(10) and R − ξ = 0.850(5). These results can be compared with those obtained from other theoretical methods, such as field theoretic methods o...

The phase transition for the (2 + 1)-dimensional spin-S = 1 XY model was investigated numerically. Because of the boson-vortex duality, the spin stiffness ρs in the ordered phase and the vortexcondensate stiffness ρv in the disordered phase should have a close relationship. We employed the exact diagonalization method, which yields the excitation gap directly. As a result, we estimate the ampli...

CONCLUSIONS Our results suggest that summating potential/action potential (SP/AP) area ratio may not necessarily have higher sensitivity in the diagnosis of endolymphatic hydrops of Meniere's disease (MD) than SP/AP amplitude ratio in transtympanic electrocochleography (ECochG). OBJECTIVE Recent studies suggested that SP/AP area curve ratio was more sensitive to endolymphatic hydrops in compa...

We study the influence of boundary conditions on the finite-size corrections of a one-dimensional (1D) quantum spin model by exact and perturbative theoretic calculations. We obtain two new infinite sets of universal amplitude ratios for the finite-size correction terms of the 1D quantum spin model of N sites with free and antiperiodic boundary conditions. The results for the lowest two orders ...

λφ theory at finite temperature suffers from infrared divergences near the temperature at which the symmetry is restored. These divergences are handled using renormalization group methods. Flow equations which use a fiducial mass as flow parameter are well adapted to predicting the non-trivial critical exponents whose presence is reflected in these divergences. Using a fiducial temperature as f...

Let fN and ξ −1 N represent, respectively, the free energy per spin and the inverse correlation length of the critical Ising model on N × ∞ lattice, with fN → f∞ as N → ∞. We obtain analytic expressions for ak and bk in the expansions: N(fN − f∞) = ∑ ∞ k=1 ak/N 2k−1 and ξ N = ∑ ∞ k=1 bk/N 2k−1 for square, honeycomb, and planetriangular lattices, and find that bk/ak = (2 2k−1)/(22k−1−1) for all ...

Spin Density Matrix Elements (SDMEs) describing the angular distribution of exclusive ρ 0 elec-troproduction and decay are determined in the HERMES experiment with 27.5 GeV beam energy on unpolarized hydrogen and deuterium targets. Those are extracted in the kinematic region 1 < Q 2 < 7 GeV 2 , 3 < W < 6.3 GeV, and −t < 0.4 GeV 2. Within the given experimental uncertainties , a hierarchy of rel...

Monte Carlo (MC) simulations and series expansion (SE) data for the energy, specific heat, magnetization and susceptibility of the ferromagnetic 4-state Potts model on the square lattice are analyzed in a vicinity of the critical point in order to estimate universal combinations of critical amplitudes. The quality of the fits is improved using predictions of the renormalization group (RG) appro...

B̄ → Dπ, Dπ, J/ψK̄ and J/ψπ decays are studied by decomposing their amplitude into a sum of factorizable and non-factorizable ones. The former is estimated by using the naive factorization while the latter is calculated by using a hard pion approximation in the infinite momentum frame. Although experiments provide only upper bounds of the branching ratios for the color suppressed B̄0 → D0π0 and D∗...