Papers by lautaro vergara
Optica Applicata, 2017
We have measured the velocity of a highly nonlinear solitary wave, generated by the collision of ... more We have measured the velocity of a highly nonlinear solitary wave, generated by the collision of a ball with a linear set of pre-compressed balls of the same material, using a double Michelson interferometer. One of the mirrors of each interferometer was mounted on one of two balls of the array. The measured soliton velocity was u = (346 ± 40) m/s for brass balls with pre-compression force F = (0.8 ± 0.1) N, and u = (102 ± 3) m/s for Teflon balls with pre-compression force F = (0.4 ± 0.1) N.
Physics of Fluids, 2019
A highly nonlinear solitary wave is generated by impacting a dry chain of beads on one of its end... more A highly nonlinear solitary wave is generated by impacting a dry chain of beads on one of its ends. Its speed depends on the speed v0 of the striker and the details of the contact force. The force on the bead at the site n = 7 and the end of the chain, as well as the time-of-flight (ToF) of both, the incident and reflected waves, is measured as a function of v0. This study was performed on a chain of stainless steel beads in two general cases: the dry chain and wet chains having three different types of oil on and around the contact points between the beads. The ToF displays a complex dependence on the fluid’s rheological properties not seen in previous studies. Power-law dependencies of the ToF on v0 in both, dry and wet, cases were found. It turned out that the Hertz plus viscoelastic interactions are not enough to account for the measured data. Two phenomenological models providing a unified and accurate account of our results were developed.
How Dissipative Highly Non-linear Solitary Waves Interact with Boundaries in a 1D Granular Medium
Springer Proceedings in Physics, 2015
Physical Review E Statistical Nonlinear and Soft Matter Physics, Jul 1, 2006
In granular media, the characterization of the behavior of solitary waves around interfaces is of... more In granular media, the characterization of the behavior of solitary waves around interfaces is of importance in order to look for more applications of these systems. We study the behavior of solitary waves at both interfaces of a symmetric granular container, a class of systems that has received recent attention because it possesses the feature of energy trapping. Hertzian contact is assumed. We have found that the scattering process is elastic at one interface, while at the other interface it is observed that the transmitted solitary wave has stopped its movement during a time that gets longer when the ratio between masses at the interfaces increases. The origin of this effect can be traced back to the phenomenon of gaps opening, recently observed experimentally.
It is shown that the phenomenon of self-similarity appears in granular media, with an intergrain ... more It is shown that the phenomenon of self-similarity appears in granular media, with an intergrain potential $V \propto \delta^{p+1}$, $p > 1$, where $\delta$ is the overlap between the grains. Although this fact can be traced back in the literature, this has not been put explicitly.
A detailed numerical study of the scattering of solitary waves by a barrier, in a granular media ... more A detailed numerical study of the scattering of solitary waves by a barrier, in a granular media with Hertzian contact, shows the existence of secondary multipulse structures generated at the interface of two "sonic vacua", which have a similar structure as the one previously found by Nesterenko and coworkers.
We present a novel way to compute the one-loop ring-improved effective potential numerically, whi... more We present a novel way to compute the one-loop ring-improved effective potential numerically, which avoids the spurious appearence of complex expressions and at the same time is free from the renormalization ambiguities of the self-consistent approaches, based on the direct application of Schwinger-Dyson type equations to the masses.
Baryon asymmetry persistence in the standard model with a singlet
Phys Rev D, 1997
We carefully review the possibility of avoiding baryon washout in the context of the standard mod... more We carefully review the possibility of avoiding baryon washout in the context of the standard model with a complex scalar singlet. Baryon asymmetry persistence occurs even for a Higgs boson mass of 80 GeV, and top-quark masses around 180 GeV.
Generalized universality, as recently proposed, postulates a universal non-Gaussian form of the p... more Generalized universality, as recently proposed, postulates a universal non-Gaussian form of the probability density function (PDF) of certain global observables for a wide class of highly correlated systems of finite volume N. Studying the 2D XY -model, we link its validity to renormalization group properties. It would be valid if there were a single dimension 0 operator, but the actual existence of several such operators leads to T-dependent corrections. The PDF is the Fourier transform of the partition function Z(q) of an auxiliary theory which differs by a dimension 0 perturbation with a very small imaginary coefficient iq/N from a theory which is asymptotically free in the infrared. We compute the PDF from a systematic loop expansion of ln Z(q).
Open Physics, 2013
By means of systematic simulations, we study the motion of discrete solitons in weakly dissipativ... more By means of systematic simulations, we study the motion of discrete solitons in weakly dissipative Toda lattices (TLs) with periodic boundary conditions, resonantly driven by a spatially staggered time-periodic (ac) force. A complex set of alternating stability bands and instability gaps, including scattered isolated stability points, is revealed in the parametric plane of the soliton's velocity and forcing amplitude for a given size of the circular lattice. The analysis is also reported for the circular TL including a single light-or heavymass defect. The stability chart as a whole shrinks and eventually disappears with the increase of the lattice's size and strength of the mass defect. Qualitative explanations to these findings are proposed. We also report the dependence of the stability area on the initial position of the soliton, finding that the area is largest for some intersite position. For a pair of solitons traveling in opposite directions, there exist regimes where both solitons survive periodic collisions in small-size lattices.
Physical Review Letters, 2005
A detailed numerical study of the scattering of solitary waves by a barrier, in a granular media ... more A detailed numerical study of the scattering of solitary waves by a barrier, in a granular media with Hertzian contact, shows the existence of secondary multipulse structures generated at the interface of two "sonic vacua", which have a similar structure as the one previously found by Nesterenko and coworkers.
Physical Review E, 2006
In granular media, the characterization of the behavior of solitary waves around interfaces is of... more In granular media, the characterization of the behavior of solitary waves around interfaces is of importance in order to look for more applications of these systems. We study the behavior of solitary waves at both interfaces of a symmetric granular container, a class of systems that has received recent attention because it posses the feature of energy trapping. Hertzian contact is assumed. We have found that the scattering process is elastic at one interface, while at the other interface it is observed that the transmitted solitary wave has stopped its movement during a time that gets longer when the ratio between masses at the interfaces increases. The origin of this effect can be traced back to the phenomenon of gaps opening, recently observed experimentally. PACS numbers: 46.40.Cd; 45.70.-n; 47.20.Ky
Physical Review E, 2008
The motion of solitons is studied in the Toda lattice with a local defect due to a change in coup... more The motion of solitons is studied in the Toda lattice with a local defect due to a change in coupling constants. We demonstrate that the generation of the trapped defect mode by the incident soliton is strongly suppressed under a certain condition. The effect is explained by the fact that, under this condition, the defect mode vanishes in the linear limit. In the same case, the soliton remains stable, traveling through a periodic array of defects; otherwise, it decays.
Physical Review E, 2005
Generalized universality, as recently proposed, postulates a universal non-Gaussian form of the p... more Generalized universality, as recently proposed, postulates a universal non-Gaussian form of the probability density function (PDF) of certain global observables for a wide class of highly correlated systems of finite volume N . Studying the 2D XY -model, we link its validity to renormalization group properties. It would be valid if there were a single dimension 0 operator, but the actual existence of several such operators leads to T -dependent corrections. The PDF is the Fourier transform of the partition function Z(q) of an auxiliary theory which differs by a dimension 0 perturbation with a very small imaginary coefficient iq/N from a theory which is asymptotically free in the infrared. We compute the PDF from a systematic loop expansion of ln Z(q).
Baryon asymmetry persistence in the standard model with a singlet
Physical Review D, 1997
ABSTRACT We carefully review the possibility of avoiding baryon washout in the context of the sta... more ABSTRACT We carefully review the possibility of avoiding baryon washout in the context of the standard model with a complex scalar singlet. Baryon asymmetry persistence occurs even for a Higgs boson mass of 80 GeV, and top-quark masses around 180 GeV.
Nuclear Physics B, 1993
The flow equations or exact RG equations for the Higgs Top System are solved to leading order in ... more The flow equations or exact RG equations for the Higgs Top System are solved to leading order in 1/N c . This allows to relate arbitrary bare actions with this field content continuously to effective low energy theories, and we find the flow converging towards general renormalizable models. The assumption of a bare action of the generalized Nambu-Jona-Lasinio type does not restrict the parameters of the low energy theory.
Modern Physics Letters A, 1996
We present a novel way to compute the one-loop ring-improved effective potential numerically, whi... more We present a novel way to compute the one-loop ring-improved effective potential numerically, which avoids the spurious appearence of complex expressions and at the same time is free from the renormalization ambiguities of the self-consistent approaches, based on the direct application of Schwinger-Dyson type equations to the masses.
Modelling high temperatures on the lattice
Journal of Physics G: Nuclear and Particle Physics, 1990
ABSTRACT The authors propose a new method to study lattice field theories at very high temperatur... more ABSTRACT The authors propose a new method to study lattice field theories at very high temperatures which overcomes the limitations of conventional schemes. The method is presented using a phi 4 theory in 3+1 dimensions, evaluated to one loop order in a renormalization group improved perturbation theory.
Evaluating one-loop integrals at finite temperature
Journal of Physics A: Mathematical and General, 1997
ABSTRACT Generic one-loop integrals at finite temperature, appearing in integrations over non-sta... more ABSTRACT Generic one-loop integrals at finite temperature, appearing in integrations over non-static modes, are given a definite expression in terms of series in powers of 0305-4470/30/19/031/img1, where m is a mass parameter and T is the temperature.
Study of floating zone profiles in materials grown by the laser-heated pedestal growth technique under isostatic atmosphere
Crystal Research and Technology, 2004
Abstract The analysis of the melt profile in floating zone techniques has been made in the past y... more Abstract The analysis of the melt profile in floating zone techniques has been made in the past years by raising differential equations in terms of Cartesian coordinates and numerically looking for its solution. Although this method permits to establish quite good ...
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Papers by lautaro vergara