Kink-antikink interactions in the double sine-Gordon equation and the problem of resonance frequencies

We studied the kink-antikink collision process for the "double sine-Gordon" (DSG) equation in 1+1 dimensions at different values of the potential parameter $R>0$. For small values of $R$ we discuss the problem of resonance frequencies. We give qualitative explanation of the frequency shift in comparison with the frequency of the discrete level in the potential well of isolated kink. We show that in this region of the parameter $R$ the effective long-range interaction between kink and antikink takes place.Comment: 9 pages, LaTeX, 4 figures (eps

Entanglement enhancement and postselection for two atoms interacting with thermal light

The evolution of entanglement for two identical two-level atoms coupled to a resonant thermal field is studied for two different families of input states. Entanglement enhancement is predicted for a well defined region of the parameter space of one of these families. The most intriguing result is the possibility of probabilistic production of maximally entangled atomic states even if the input atomic state is factorized and the corresponding output state is separable.Comment: accepted for publication in J. Phys.

Comment on The Evidence for a Pentaquark and Kinematic Reflections

The Regge exchange model used by Dzierba et al. is shown to be questionable, since the pion pole term is not allowed. Hence the Regge amplitudes in their calculation are exaggerated. The amount of kinematic reflection in the mass spectrum of the (nK+) system, which is one decay channel of a possible pentaquark, is not well justified in the fitting procedure used by Dzierba et al., as shown by comparison with the (K+K-) invariant mass spectrum, which is one decay channel of the a_2 and f_2 tensor mesons. While kinematic reflections are still a concern in some papers that have presented evidence for the pentaquark, better quantitative calculations are needed to demonstrate the significance of this effect.Comment: Comment submitted to Phys. Rev. D (no figures

Off-line studies of the laser ionization of yttrium at the IGISOL facility

A laser ion source is under development at the IGISOL facility, Jyvaskyla, in order to address deficiencies in the ion guide technique. The key elements of interest are those of a refractory nature, whose isotopes and isomers are widely studied using both laser spectroscopic and high precision mass measurement techniques. Yttrium has been the first element of choice for the new laser ion source. In this work we present a new coupled dye-Ti:Sapphire laser scheme and give a detailed discussion of the results obtained from laser ionization of yttrium atoms produced in an ion guide via joule heating of a filament. The importance of not only gas purity, but indeed the baseline vacuum pressure in the environment outside the ion guide is discussed in light of the fast gas phase chemistry seen in the yttrium system. A single laser shot model is introduced and is compared to the experimental data in order to extract the level of impurities within the gas cell.Comment: 18 pages submitted to NIM

Effect of microstructure state of titanium alloy Ti-6Al-4V on structure and mechanical properties of joints produced by diffusion bonding process

The studies of diffusion bonded samples of Ti-6Al-4V and Nitinol alloys were carried out considering the titanium alloy in two states: ultra-fine grained and bi-modal microstructures, the last one consisted of small and large a-phase grains. Depending on microstructure and chemical composition of the alloys, the diffusion bonding had been made at temperatures from 600°C to 850°C. The microstructures of joints was studied by scanning electron microscope using detector of backscattering electron diffraction. The shear strengths of joints were measured. It was concluded that the ultra-fine grained Ti-6Al-4V alloy could be applied for joints manufactured at a temperature lower than 750°C. The bi-modal Ti-6Al-4V alloy is an effective material for producing the joints at the temperature larger that 750°

The evolution of the structure and mechanical properties of aluminum during accumulative roll bonding

The dependence of microstructure, microhardness, and strength properties in tensile strain tests of commercially pure aluminum on strain during accumulative roll-bonding was studied. The methods of transmission electron microscopy and electron back scattered diffraction patterns analysis were used to establish that a lamellar ultrafine structure is formed in aluminum after accumulative roll bonding. The reasons for the difference in the structure and mechanical properties of the aluminum studied from the ones relevant for the aluminum deformed by equalchannel angular pressing are discusse