Search results for "BREAKING"
showing 10 items of 383 documents
Unitarity constraints on resonance mixing and the Okubo-Zweig-Iizuka rule
1978
We discuss unitarity constraints on the (complex) mixing angle (δ) between resonances. In particular, when the mixing is small, as when it is forbidden by the Okubo-Zweig-Iizuka (OZI) rule, or some other mechanism, one can derive useful bounds on δ or determine Arg (δ) from the data of allowed decays of the resonances. In the case of f′−f mixing the unitarity bound |δ|≳0.05±0.015 is barely compatible with the experimental f′←ππ rate (if one assumes that it is dominated by f′←f←ππ transition). Furthermore, experimentally Im δ≈0 which together with unitarity gives Re δ=−0.08±0.03, in clear discrepancy with the observed f′←ππ rate. This suggests that the mixing of f′ with higher f-like recurre…
Isospin mixing in nuclei within the nuclear density functional theory.
2009
We present the self-consistent, non-perturbative analysis of isospin mixing using the nuclear density functional approach and the rediagonalization of the Coulomb interaction in the good-isospin basis. The largest isospin-breaking effects are predicted for N = Z nuclei and they quickly fall with the neutron excess. The unphysical isospin violation on the mean-field level, caused by the neutron excess, is eliminated by the proposed method. We find a significant dependence of the magnitude of isospin breaking on the parametrization of the nuclear interaction term. A rough correlation has been found between the isospin mixing parameter and the difference of proton and neutron rms radii. The th…
Novel stripe textures in nonchiral hexatic liquid-crystal films
1992
A novel macroscopic stripe texture has been observed in freely suspended films of nonchiral liquid crystal, uniform stripes of alternating molecular orientation form spontaneously at the smectic-C--to--surface-hexatic phase transition and broaden with decreasing temperature. The stripes are identified as splay domains whose formation is attributed to the polar symmetry of the hexatic surface layers. Transverse (director bend) walls, which lead to an additional modulation of the basic one-dimensional pattern, are manifested inside thick circular islands as twelve-armed star defects.
Monte Carlo Methods: a powerful tool of statistical physics
1998
Statistical mechanics of condensed matter systems (solids, fluids) tries to express macroscopic equilibrium properties of matter as averages computed from a Hamiltonian that expresses interactions of an atomistic many body system. While analytic methods for most problems involve crude and uncontrolled approximations, the Monte Carlo computer simulation method allows a numerically exact treatment of this problem, apart from “statistical errors” which can be made as small as desired, and the systematic problem that a system of finite size is treated rather than the thermodynamic limit. However, the simulations of phase transitions then elucidate how a symmetry breaking arises via breaking of …
Composite states of two right-handed neutrinos
2016
In this work, we develop a model for Higgs-like composites based on two generations of right-handed neutrinos that condense. We analyze the spontaneous symmetry breaking of the theory with two explicit breakings, setting the different scales of the model and obtaining massive bosons as a result. Finally, we calculate the gravitational wave imprint left by the phase transition associated with the symmetry breaking of a generic potential dictated by the symmetries of the composites.
Noncritical generation of nonclassical frequency combs via spontaneous rotational symmetry breaking
2016
Synchronously pumped optical parametric oscillators (SPOPOs) are optical cavities containing a nonlinear crystal capable of down-converting a frequency comb to lower frequencies. These have received a lot of attention lately, because their intrinsic multimode nature makes them compact sources of quantum correlated light with promising applications in modern quantum information technologies. In this work we show that SPOPOs are also capable of accessing the challenging but interesting regime where spontaneous symmetry breaking plays a crucial role in the quantum properties of the emitted light, difficult to access with any other nonlinear optical cavity. Apart from opening the possibility of…
Perturbative QCD study of Bs decays to a pseudoscalar meson and a tensor meson
2014
We study two-body hadronic B-s -> PT decays, with P(T) being a light pseudoscalar (tensor) meson, in the perturbative QCD approach. The CP-averaged branching ratios and the direct CP asymmetries of the Delta S = 0 modes are predicted, where Delta S is the difference between the strange numbers of final and initial states. We also define and calculate experimental observables for the Delta S = 1 modes under the B-s(0)-(B) over bar (0)(s) mixing, including CP averaged branching ratios, time-integrated CP asymmetries, and the CP observables C-f, D-f and S-f. Results are compared to the B-s -> PV ones in the literature, and to the B -> PT ones, which indicate considerable U-spin symmetry breaki…
Noncritically squeezed light via spontaneous rotational symmetry breaking.
2007
We theoretically address squeezed light generation through the spontaneous breaking of the rotational invariance occuring in a type I degenerate optical parametric oscillator (DOPO) pumped above threshold. We show that a DOPO with spherical mirrors, in which the signal and idler fields correspond to first order Laguerre-Gauss modes, produces a perfectly squeezed vacuum with the shape of a Hermite-Gauss mode, within the linearized theory. This occurs at any pumping level above threshold, hence the phenomenon is non-critical. Imperfections of the rotational symmetry, due e.g. to cavity anisotropy, are shown to have a small impact, hence the result is not singular.
Spontaneous symmetry breaking as a resource for noncritically squeezed light
2010
[EN] In the last years we have proposed the use of the mechanism of spontaneous symmetry breaking with the purpose of generating perfect quadrature squeezing. Here we review previous work dealing with spatial (translational and rotational) symmetries, both on optical parametric oscillators and four-wave mixing cavities, as well as present new results. We then extend the phenomenon to the polarization state of the signal field, hence introducing spontaneous polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in which the phenomenon can be investigated at the singlephoton-pair level in a non-dissipative case, with the purpose of understanding it from a most fundamental …
The massive analytic invariant charge in QCD
2004
The low energy behavior of a recently proposed model for the massive analytic running coupling of QCD is studied. This running coupling has no unphysical singularities, and in the absence of masses displays infrared enhancement. The inclusion of the effects due to the mass of the lightest hadron is accomplished by employing the dispersion relation for the Adler D function. The presence of the nonvanishing pion mass tames the aforementioned enhancement, giving rise to a finite value for the running coupling at the origin. In addition, the effective charge acquires a "plateau-like" behavior in the low energy region of the timelike domain. This plateau is found to be in agreement with a number…