Behavior of tumors under nonstationary theraphy

We present a model for the interaction dynamics of lymphocytes-tumor cells population. This model reproduces all known states for the tumor. Futherly,we develop it taking into account periodical immunotheraphy treatment with cytokines alone. A detailed analysis for the evolution of tumor cells as a function of frecuency and theraphy burden applied for the periodical treatment is carried out. Certain threshold values for the frecuency and applied doses are derived from this analysis. So it seems possible to control and reduce the growth of the tumor. Also, constant values for cytokines doses seems to be a succesful treatment.Comment: 6 pages, 7 figure

Nature of 45 degree vortex lattice reorientation in tetragonal superconductors

The transformation of the vortex lattice in a tetragonal superconductor which consists of its 45 degree reorientation relative to the crystal axes is studied using the nonlocal London model. It is shown that the reorientation occurs as two successive second order (continuous) phase transitions. The transition magnetic fields are calculated for a range of parameters relevant for borocarbide superconductors in which the reorientation has been observed

Consistency in Regularizations of the Gauged NJL Model at One Loop Level

In this work we revisit questions recently raised in the literature associated to relevant but divergent amplitudes in the gauged NJL model. The questions raised involve ambiguities and symmetry violations which concern the model's predictive power at one loop level. Our study shows by means of an alternative prescription to handle divergent amplitudes, that it is possible to obtain unambiguous and symmetry preserving amplitudes. The procedure adopted makes use solely of {\it general} properties of an eventual regulator, thus avoiding an explicit form. We find, after a thorough analysis of the problem that there are well established conditions to be fulfiled by any consistent regularization prescription in order to avoid the problems of concern at one loop level.Comment: 22 pages, no figures, LaTeX, to appear in Phys.Rev.

Updating the Phase Diagram of the Gross-Neveu Model in 2+1 Dimensions

The method of optimized perturbation theory (OPT) is used to study the phase diagram of the massless Gross-Neveu model in 2+1 dimensions. In the temperature and chemical potential plane, our results give strong support to the existence of a tricritical point and line of first order phase transition, previously only suspected to exist from extensive lattice Monte Carlo simulations. In addition of presenting these results we discuss how the OPT can be implemented in conjunction with the Landau expansion in order to determine all the relevant critical quantities.Comment: 7 pages, 2 eps figures. Replaced with the version that matches the published one (PLB

Identificación y compensación del sesgo en sensores inerciales MEMS de muy bajo costo mediante el uso de algoritmos de aprendizaje automático

En los últimos años, el uso de sensores inerciales basados en tecnología MEMS (MicroElectroMechanical Systems) se ha consolidado en diferentes áreas que requieren sensores baratos, livianos y de bajo consumo de energía. Algunas de estas áreas son la robótica móvil aérea y la robótica móvil terrestre. Una desventaja que presentan este tipo de sensores es su bajo desempeño comparado con sensores fabricados con otras tecnologías. Los dos errores más gravitantes en el desempeño de un sensor inercial MEMS son el ruido blanco y el sesgo presentes en la señal de salida del sensor. En particular, el sesgo presenta una variación no lineal muy notoria respecto a la temperatura, debido a que los sensores MEMS están construidos mayoritariamente con silicio. En la literatura existente, si bien se encuentran varios trabajos que han tratado de corregir el sesgo en sensores inerciales MEMS utilizando técnicas basadas en aprendizaje automático (machine learning), debido a la naturaleza no lineal del fenómeno que se trata de predecir, todos estos trabajos han utilizado sensores MEMS cuyo costo varía entre los USD 300 y los USD 1.000. En los últimos años han surgido sensores inerciales MEMS de muy bajo costo, los cuales se encuentran en una cantidad importante de sistemas robóticos. El costo de estos sensores ronda los USD 10. En este trabajo se propone analizar y compensar las variaciones del sesgo por temperatura en sensores inerciales MEMS de muy bajo costo, usando diferentes técnicas de aprendizaje automático. La hipótesis central de este proyecto se basa en mejorar el rendimiento de sensores inerciales de muy bajo costos aplicando técnicas de aprendizaje automático del estado del arte, las cuales permitirán identificar la relación no lineal que existe entre el sesgo y la temperatura.Red de Universidades con Carreras en Informátic

Small oscillations of a chiral Gross-Neveu system

We study the small oscillations regime (RPA approximation) of the time-dependent mean-field equations, obtained in a previous work, which describe the time evolution of one-body dynamical variables of a uniform Chiral Gross-Neveu system. In this approximation we obtain an analytical solution for the time evolution of the one-body dynamical variables. The two-fermion physics can be explored through this solution. The condition for the existence of bound states is examined.Comment: 21pages, Latex, 1postscript figur

Effective potential for composite operators and for an auxiliary scalar field in a Nambu-Jona-Lasinio model

We derive the effective potentials for composite operators in a Nambu-Jona-Lasinio (NJL) model at zero and finite temperature and show that in each case they are equivalent to the corresponding effective potentials based on an auxiliary scalar field. The both effective potentials could lead to the same possible spontaneous breaking and restoration of symmetries including chiral symmetry if the momentum cutoff in the loop integrals is large enough, and can be transformed to each other when the Schwinger-Dyson (SD) equation of the dynamical fermion mass from the fermion-antifermion vacuum (or thermal) condensates is used. The results also generally indicate that two effective potentials with the same single order parameter but rather different mathematical expressions can still be considered physically equivalent if the SD equation corresponding to the extreme value conditions of the two potentials have the same form.Comment: 7 pages, no figur

Experimental observation of high field diamagnetic fluctuations in Niobium

We have performed a magnetic study of a bulk metallic sample of Nb with critical temperature $T_{c}=8.5$ K. Magnetization versus temperature (M {\it vs} T) data obtained for fixed magnetic fields above 1 kOe show a superconducting transition which becomes broader as the field is increased. The data are interpreted in terms of the diamagnetic lowest Landau level (LLL) fluctuation theory. The scaling analysis gives values of the superconducting transition temperature $T_{c}(H)$ consistent with $H_{c2}(T)$% . We search for universal 3D LLL behavior by comparing scaling results for Nb and YBaCuO, but obtain no evidence for universality.Comment: 5 pages, 6 figures, Accepted for publication in Phys.Rev.

Enhancement of the superconducting transition temperature from the competition between electron-electron correlations and electron-phonon interactions

We uncover that the competition between electron-electron correlations and electron-phonon interactions gives rise to unexpectedly huge enhancement of the superconducting transition temperature, several hundreds percent larger ($\geq$ 200 K) than that of the case when only one of the two is taken into account ($\sim$ 30 K). Our renormalization group analysis claims that this mechanism for the enhancement of the critical temperature is not limited on superconductivity but applied to various Fermi surface instabilities, proposing an underlying universal structure, which turns out to be essentially identical to that of a recent study [Phys. Rev. Lett. {\bf 108}, 046601 (2012)] on the enhancement of the Kondo temperature in the presence of Rashba spin-orbit interactions. We also discuss the stability of superconductivity against nonmagnetic randomness

Towards an Asymptotic-Safety Scenario for Chiral Yukawa Systems

We search for asymptotic safety in a Yukawa system with a chiral $U(N_L)_L\otimes U(1)_R$ symmetry, serving as a toy model for the standard-model Higgs sector. Using the functional RG as a nonperturbative tool, the leading-order derivative expansion exhibits admissible non-Ga\ssian fixed-points for $1 \leq N_L \leq 57$ which arise from a conformal threshold behavior induced by self-balanced boson-fermion fluctuations. If present in the full theory, the fixed-point would solve the triviality problem. Moreover, as one fixed point has only one relevant direction even with a reduced hierarchy problem, the Higgs mass as well as the top mass are a prediction of the theory in terms of the Higgs vacuum expectation value. In our toy model, the fixed point is destabilized at higher order due to massless Goldstone and fermion fluctuations, which are particular to our model and have no analogue in the standard model.Comment: 16 pages, 8 figure