Solutions of the dispersion equation in the region of overlapping of zero-sound and particle-hole modes

In this paper the solutions of the zero-sound dispersion equation in the random phase approximation (RPA) are considered. The calculation of the damped zero-sound modes \omega_s(k) (complex frequency of excitation) in the nuclear matter is presented. The method is based on the analytical structure of the polarization operators \Pi(\omega,k). The solutions of two dispersion equations with \Pi(\omega,k) and with Re(\Pi(\omega,k)) are compared. It is shown that in the first case we obtain one-valued smooth solutions without "thumb-like" forms. Considering the giant resonances in the nuclei as zero-sound excitations we compare the experimental energy and escape width of the giant dipole resonance (GDR) in the nucleus A with \omega_s(k) taken at a definite wave vector k=k_A.Comment: 14 pages, 5 figures; revised versio

Supercontinuum Generation over 2 µm

Effective supercontinuum generation in fiber mediain spectral range over 2 μm was experimentallydemonstrated. Supercontinuum generation wasobserved in passive optical fibers. Maximumspectral broadening was obtained in germaniumdopedfibers with longest wavelength near 2.7 μm.To provide high spectral density we used opticalfiber amplifiers. Thus supercontinuum generationwas obtained in holmium optical fiber amplifiersmedium with spectral density 10 W/nm, in therange from 2 to 2.5 μm. In thulium fiber amplifiersobserved amplification not only in conventionalrange near 1.8 μm, but in spectral range from 2.3 to2.5 μm, that corresponds to 3H4→ 3H5 opticaltransition possibility in thulium-doped opticalfibers

QCD condensates and hadron parameters in nuclear matter: self-consistent treatment, sum rules and all that

We review various approaches to the calculation of QCD condensates and of the nucleon characteristics in nuclear matter. We show the importance of their self-consistent treatment. The first steps in such treatment appeared to be very instructive. It is shown that the alleged pion condensation anyway can not take place earlier than the restoration of the chiral symmetry. We demonstrate how the finite density QCD sum rules for nucleons work and advocate their possible role in providing an additional bridge between the condensate and hadron physics.Comment: 67 pages, LaTeX, 15 figures, epsfig.sty; to be published in "Progress in Particle and Nuclear Physics", vol.47, is.

Self-consistent treatment of the quark condensate and hadrons in nuclear matter

We calculate the contribution of pions to the $\bar qq$-expectation value $\kappa(\rho)= \langle M|\bar qq|M\rangle$ in symmetric nuclear matter. We employ exact pion propagator renormalized by nucleon-hole and isobar-hole excitations. Conventional straightforward calculation leads to the “pion condensation" at unrealistically small values of densities, causing even earlier restoration of chiral symmetry. This requires a self-consistent approach, consisting in using the models, which include direct dependence of in-medium mass values on $\kappa(\rho)$, e.g. the Nambu–Jona-Lasinio–model. We show, that in the self-consistent approach the $\rho$-dependence of the condensate is described by a smooth curve. The “pion condensate" point is removed to much higher values of density. The chiral restoration does not take place at least while $\rho<2.8\rho_0$ with $\rho_0$ being the saturation value. Validity of our approach is limited by possible accumulation of heavier baryons (delta isobars) in the ground state of nuclear matter. For the value of effective nucleon mass at the saturation density we found $m^*(\rho_0)=0.6m$, consistent with nowadays results of other authors

РАЗРАБОТКА УНИВЕРСАЛЬНОГО ОПТИЧЕСКОГО СТЕНДА ДЛЯ ИЗМЕРЕНИЯ ДИНАМИКИ НАСЫЩЕНИЯ ПОГЛОЩЕНИЯ ОПТИЧЕСКИХ ПОГЛОТИТЕЛЕЙ

A universal stand for measuring the saturation absorption dynamics of optical absorbers has been created. The presented setup allows to carry out real-time measurements, as well as adjusting the heat load on the sample by changing the duty cycle and frequency of complex pulses.Создан универсальный стенд для измерения динамики насыщения поглощения оптических поглотителей. Представленная установка позволяет проводить измерения в реальном времени, а также регулировать тепловую нагрузку на образец изменением скважности и частоты импульсов сложной формы