The Barbero-Immirzi Parameter as a Scalar Field: K-Inflation from Loop Quantum Gravity?

We consider a loop-quantum gravity inspired modification of general relativity, where the Holst action is generalized by making the Barbero-Immirzi (BI) parameter a scalar field, whose value could be dynamically determined. The modified theory leads to a non-zero torsion tensor that corrects the field equations through quadratic first-derivatives of the BI field. Such a correction is equivalent to general relativity in the presence of a scalar field with non-trivial kinetic energy. This stress-energy of this field is automatically covariantly conserved by its own dynamical equations of motion, thus satisfying the strong equivalence principle. Every general relativistic solution remains a solution to the modified theory for any constant value of the BI field. For arbitrary time-varying BI fields, a study of cosmological solutions reduces the scalar field stress-energy to that of a pressureless perfect fluid in a comoving reference frame, forcing the scale factor dynamics to be equivalent to those of a stiff equation of state. Upon ultraviolet completion, this model could provide a natural mechanism for k-inflation, where the role of the inflaton is played by the BI field and inflation is driven by its non-trivial kinetic energy instead of a potential.Comment: Phys. Rev. D78, 064070 (2008

Extreme Mass-Ratio Inspirals in the Effective-One-Body Approach: Quasi-Circular, Equatorial Orbits around a Spinning Black Hole

We construct effective-one-body waveform models suitable for data analysis with LISA for extreme-mass ratio inspirals in quasi-circular, equatorial orbits about a spinning supermassive black hole. The accuracy of our model is established through comparisons against frequency-domain, Teukolsky-based waveforms in the radiative approximation. The calibration of eight high-order post-Newtonian parameters in the energy flux suffices to obtain a phase and fractional amplitude agreement of better than 1 radian and 1 % respectively over a period between 2 and 6 months depending on the system considered. This agreement translates into matches higher than 97 % over a period between 4 and 9 months, depending on the system. Better agreements can be obtained if a larger number of calibration parameters are included. Higher-order mass ratio terms in the effective-one-body Hamiltonian and radiation-reaction introduce phase corrections of at most 30 radians in a one year evolution. These corrections are usually one order of magnitude larger than those introduced by the spin of the small object in a one year evolution. These results suggest that the effective-one-body approach for extreme mass ratio inspirals is a good compromise between accuracy and computational price for LISA data analysis purposes.Comment: 21 pages, 8 figures, submitted to Phys. Rev.

Comparación de diferentes parámetros de evaluación en sujetos con asma moderada estable sin exacerbación microbiana, tratados con Salmeterol-Fluticasona vs Ciclesonida y Salbutamol a demanda

El asma es una entidad clínica caracterizada por la combinación de tres factores: obstrucción de la vía aérea con reversibilidad espontánea y/o farmacológica, hiperrreactividad bronquial e inflamación local. Existen numerosas alternativas farmacológicas para el tratamiento de esta enfermedad. En el presente trabajo se compararon parámetros de evaluación del estado asmático moderado, los episodios de exacerbación de etiología bacteriana y la colonización bucal por hongos en dos grupos de pacientes; 15 tratados con ciclesonida en dosis alta y salbutamol a demanda y 13 con salmeterol fluticasona en dosis fija durante 300 días de tratamiento. Hasta el momento se observó que ambas alternativas terapéuticas son válidas para el control de la enfermedad, ya que a pesar de la presencia en esputo, de bacterias potencialmente capaces de producir exacerbaciones, estas no ocurrieron durante el tiempo del estudio. La colonización por hongos de la cavidad oral se presentó en ambos grupos. Los parámetros de función pulmonar fueron comparables.Fil: Sagua, M.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área MicrobiologíaFil: Elías, P.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Telechea, A.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área MicrobiologíaFil: Molina, A.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Clínica MédicaFil: Garófoli, A.. Hospital Militar Regional Mendoza. Servicio de NeumonologíaFil: Fazio, C.. Hospital Militar Regional Mendoza. Servicio de NeumonologíaFil: Montbrun, M.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área MicrobiologíaFil: Yunes, Roberto. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Montoya, P.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología

Metric of a tidally perturbed spinning black hole

We explicitly construct the metric of a Kerr black hole that is tidally perturbed by the external universe in the slow-motion approximation. This approximation assumes that the external universe changes slowly relative to the rotation rate of the hole, thus allowing the parameterization of the Newman-Penrose scalar $\psi_0$ by time-dependent electric and magnetic tidal tensors. This approximation, however, does not constrain how big the spin of the background hole can be and, in principle, the perturbed metric can model rapidly spinning holes. We first generate a potential by acting with a differential operator on $\psi_0$. From this potential we arrive at the metric perturbation by use of the Chrzanowski procedure in the ingoing radiation gauge. We provide explicit analytic formulae for this metric perturbation in spherical Kerr-Schild coordinates, where the perturbation is finite at the horizon. This perturbation is parametrized by the mass and Kerr spin parameter of the background hole together with the electric and magnetic tidal tensors that describe the time evolution of the perturbation produced by the external universe. In order to take the metric accurate far away from the hole, these tidal tensors should be determined by asymptotically matching this metric to another one valid far from the hole. The tidally perturbed metric constructed here could be useful in initial data constructions to describe the metric near the horizons of a binary system of spinning holes. This perturbed metric could also be used to construct waveforms and study the absorption of mass and angular momentum by a Kerr black hole when external processes generate gravitational radiation.Comment: 17 pages, 3 figures. Final PRD version, minor typos, etc corrected. v3: corrected typo in Eq. (35) and (57

Barbero-Immirzi field in canonical formalism of pure gravity

The Barbero-Immirzi (BI) parameter is promoted to a field and a canonical analysis is performed when it is coupled with a Nieh-Yan topological invariant. It is shown that, in the effective theory, the BI field is a canonical pseudoscalar minimally coupled with gravity. This framework is argued to be more natural than the one of the usual Holst action. Potential consequences in relation with inflation and the quantum theory are briefly discussed.Comment: 10 page

Testing Alternative Theories of Gravity using LISA

We investigate the possible bounds which could be placed on alternative theories of gravity using gravitational wave detection from inspiralling compact binaries with the proposed LISA space interferometer. Specifically, we estimate lower bounds on the coupling parameter \omega of scalar-tensor theories of the Brans-Dicke type and on the Compton wavelength of the graviton \lambda_g in hypothetical massive graviton theories. In these theories, modifications of the gravitational radiation damping formulae or of the propagation of the waves translate into a change in the phase evolution of the observed gravitational waveform. We obtain the bounds through the technique of matched filtering, employing the LISA Sensitivity Curve Generator (SCG), available online. For a neutron star inspiralling into a 10^3 M_sun black hole in the Virgo Cluster, in a two-year integration, we find a lower bound \omega > 3 * 10^5. For lower-mass black holes, the bound could be as large as 2 * 10^6. The bound is independent of LISA arm length, but is inversely proportional to the LISA position noise error. Lower bounds on the graviton Compton wavelength ranging from 10^15 km to 5 * 10^16 km can be obtained from one-year observations of massive binary black hole inspirals at cosmological distances (3 Gpc), for masses ranging from 10^4 to 10^7 M_sun. For the highest-mass systems (10^7 M_sun), the bound is proportional to (LISA arm length)^{1/2} and to (LISA acceleration noise)^{-1/2}. For the others, the bound is independent of these parameters because of the dominance of white-dwarf confusion noise in the relevant part of the frequency spectrum. These bounds improve and extend earlier work which used analytic formulae for the noise curves.Comment: 16 pages, 9 figures, submitted to Classical & Quantum Gravit

Extreme mass ratio inspiral rates: dependence on the massive black hole mass

We study the rate at which stars spiral into a massive black hole (MBH) due to the emission of gravitational waves (GWs), as a function of the mass M of the MBH. In the context of our model, it is shown analytically that the rate approximately depends on the MBH mass as M^{-1/4}. Numerical simulations confirm this result, and show that for all MBH masses, the event rate is highest for stellar black holes, followed by white dwarfs, and lowest for neutron stars. The Laser Interferometer Space Antenna (LISA) is expected to see hundreds of these extreme mass ratio inspirals per year. Since the event rate derived here formally diverges as M->0, the model presented here cannot hold for MBHs of masses that are too low, and we discuss what the limitations of the model are.Comment: Accepted to CQG, special LISA issu

Ultrasound-Promoted Synthesis of 3-(Thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1carboximidamides and Anticancer Activity Evaluation in Leukemia Cell Lines

3-(Thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1-carboximidamides were efficiently prepared through a cyclocondensation of thiophenylchalcones with aminoguanidine hydrochloride under ultrasonic conditions in the presence of KOH and ethanol as a green solvent in short reaction times (15-35 min) and good yields (62-95%). All compounds produced were evaluated against the human Jurkat and RS411 acute lymphoblastic leukemia cell lines of T- and B-cell origin, respectively, and the K562 myelogenous leukemia cell line. Six compounds presented half maximal inhibitory concentration (IC50) values around 15 mu mol L-1 and five compounds presented IC50 values around 40 mu mol L-1 for at least one of the three cell lines analyzed. One compound was not significantly cytotoxic, presenting IC50 value > 100 mu mol L- 1.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Fundacao de Apoio ao Desenvolvimento do Ensino, Ciencia e Tecnologia do Estado de Mato Grosso do Sul (FUNDECT)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)FAPESPCNPqFundacao Univ Fed Grande Dourados, Grp Pesquisa Sintese & Caracterizacao Mol MS, Rua Joao Rosa Goes 1761, BR-79825070 Dourados, MS, BrazilUniv Estadual Campinas, Inst Biol, Dept Genet & Biol Mol, Rua Monteiro Lobato 255, BR-13083970 Campinas, SP, BrazilCtr Infantil Boldrini, Mol Biol Lab, Rua Dr Gabriel Porto 1270, BR-13083210 Campinas, SP, BrazilUniv Fed Sao Paulo, Dept Ciencias Exatas & Terra, Rua Prof Artur Riedel 275, BR-09972270 Diadema, SP, BrazilUniv Fed Pelotas, Ctr Ciencias Quim Farmaceut & Alimentos, Lab Lipid & Bioorgan, Campus Univ, BR-96001900 Pelotas, RS, BrazilUniv Estadual Mato Grosso do Sul, Rua Emilio Mascolli 275, BR-79950000 Navirai, MS, BrazilUniv Fed Sao Paulo, Dept Ciencias Exatas & Terra, Rua Prof Artur Riedel 275, BR-09972270 Diadema, SP, BrazilCNPq: 483021/2013-0FUNDECT: 0180/12FAPESP: 12/12802-1Web of Scienc