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Hector Vucetich

Publications and source records attributed to Hector Vucetich.

At least 19 recordsLinked to original sources
arXiv2012

Constraining the fundamental interactions and couplings with Eötvös experiments

Upper bounds for the violation of the Weak Equivalence Principle (WEP) by the Fundamental Interactions have been given before. We now recompute the limits on the parameters measuring the strength of the violation with the whole set of high accuracy Eötvös experiments. Besides, limits on spatial variation of the Fundamental Constants α, Weinberg angle θ, and v, the vacuum expectation value of the Higgs field, are found in a model independent way. Limits on other parameters in the gauge sector are also found from the strucutre of the Standard Model.

gr-qc↗
arXiv2009

Thermodynamics in variable speed of light theories

The perfect fluid in the context of a covariant variable speed of light theory proposed by J. Magueijo is studied. On the one hand the modified first law of thermodynamics together with a recipe to obtain equations of state are obtained. On the other hand the Newtonian limit is performed to obtain the nonrelativistic hydrostatic equilibrium equation for the theory. The results obtained are used to determine the time variation of the radius of Mercury induced by the variability of the speed of light ($c$), and the scalar contribution to the luminosity of white dwarfs. Using a bound for the change of that radius and combining it with an upper limit for the variation of the fine structure constant, a bound on the time variation of $c$ is set. An independent bound is obtained from luminosity estimates for Stein 2015B.

astro-ph↗
arXiv2009

WMAP 5-year constraints on time variation of $α$ and $m_e$

We studied the role of fundamental constants in an updated recombination scenario, focusing on the time variation of the fine structure constant αand the electron mass m_e in the early Universe. Using CMB data including WMAP 5-yr release, and the 2dFGRS power spectrum, we put bounds on variations of these constants, when both constants are allowed to vary, and in the case that only one of them is variable. In particular, we have found that -0.019 < Δα/ α_0 < 0.017 (95% c.l.), in our joint estimation of αand cosmological parameters. Finally, we analyze how the constraints depends on the recombination scenario.

astro-ph.CO↗
arXiv2009

Brane-world cosmology and varying $G$

We consider a brane-world cosmological model coupled to a bulk scalar field. Since the brane tension turns out to be proportional to Newton coupling $G$, in such a model a time variation of $G$ naturally occurs. By resorting to available bounds on the variation of $G$, the parameters of the model are constrained. The constraints coming from nucleosynthesis and CMB result to be the severest ones.

gr-qc↗
arXiv2008

WMAP 5-year constraints on time variation of $α$ and $m_e$ in a detailed recombination scenario

We study the role of fundamental constants in an updated recombination scenario. We focus on the time variation of the fine structure constant, and the electron mass in the early Universe, and put bounds on these quantities by using data from CMB including WMAP 5-yr release and the 2dFGRS power spectrum. We analyze how the constraints are modified when changing the recombination scenario.

astro-ph↗
arXiv2008

Early Universe Constraints on Time Variation of Fundamental Constants

We study the time variation of fundamental constants in the early Universe. Using data from primordial light nuclei abundances, CMB and the 2dFGRS power spectrum, we put constraints on the time variation of the fine structure constant $α$, and the Higgs vacuum expectation value $ $ without assuming any theoretical framework. A variation in $ $ leads to a variation in the electron mass, among other effects. Along the same line, we study the variation of $α$ and the electron mass $m_e$. In a purely phenomenological fashion, we derive a relationship between both variations.

astro-ph↗
arXiv2007

Time variation of the fine structure constant in the early universe and the Bekenstein model

We calculate bounds on the variation of the fine structure constant at the time of primordial nucleosynthesis and at the time of neutral hydrogen formation. We use these bounds and other bounds from the late universe to test Bekenstein model. We modify the Kawano code, CAMB and CosmoMC in order to include the possible variation of the fine structure constant. We use observational primordial abundances of $\De$, $\He$ and $\Li$, recent data from the Cosmic Microwave Background and the 2dFGRS power spectrum, to obtain bounds on the variation of $α$. We calculate a piecewise solution to the scalar field equation of Bekenstein model in two different regimes; i) matter and radiation, ii) matter and cosmological constant. We match both solutions with appropriate boundary conditions. We perform a statistical analysis using the bounds obtained from the early universe and other bounds from the late universe to constrain the free parameters of the model. Results are consistent with no variation of $α$ in the early universe. Limits on $α$ are inconsistent with the scale length of the theory $l$ being larger than Planck scale. In order to fit all observational and experimental data, the assumption $l>L_p$ implied in Bekenstein's model has to be relaxed.

astro-ph↗
arXiv2006

Helium and Deuterium Abundances as a Test for the Time Variation of the Fine Structure Constant and the Higgs Vacuum Expectation Value

We use the semi-analytic method of \citet{Esma91} to calculate the abundances of Helium and Deuterium produced during Big Bang nucleosynthesis assuming the fine structure constant and the Higgs vacuum expectation value may vary in time. We analyze the dependence on the fundamental constants of the nucleon mass, nuclear binding energies and cross sections involved in the calculation of the abundances. Unlike previous works, we do not assume the chiral limit of QCD. Rather, we take into account the quark masses and consider the one-pion exchange potential, within perturbation theory, for the proton-neutron scattering. However, we do not consider the time variation of the strong interactions scale but attribute the changes in the quark masses to the temporal variation of the Higgs vacuum expectation value. Using the observational data of the helium and deuterium, we put constraints on the variation of the fundamental constants between the time of nucleosynthesis and the present time.

astro-ph↗
arXiv2006

Possibility of obtaining a non-relativistic proof of the spin-statistics theorem in the Galilean frame

Here we explore the possibility to obtain a non-relativistic proof of the spin-statistics theorem. First, we examine the structure of axioms and theorems involved in a relativistic Schwinger-like proof of the spin-statistics relation. Second, starting from this structure we identify the relativistic assumptions. Last, we reformulate these assumptions in order to obtain a Galilean proof. We conclude that the spin-statistics theorem cannot be deduced into the framework of Galilean quantum field theories for three space dimensions because two of the assumptions needed to prove the theorem are incompatible. We analyze, however, the conditions under which a non-relativist proof could still be deduced.

quant-ph↗
arXiv2005

Testing a string dilaton model with experimental and observational data

We test the prediction of the time variation of the fine structure constant in the string dilaton model proposed by Damour and Polyakov. First, we analize the dependence of all available observational and experimental data with the fine structure constant variation. Furthermore, we obtain the prediction of the time variation of the fine structure constant including the renormalization group correction. Finally, we use the data set to perform a statistical analyisis. This analysis enables us to determine that the the dilaton model is in agreement with most of the data. Finally, constraints on the free parameters of this model are obtained.

astro-ph↗
arXiv2005

Primordial Nucleosynthesis with varying fundamental constants: A semi-analytical approach

Using the semi-analytic method proposed by \citet{Esma91} we calculate the abundances of the light elements produced during primordial nucleosynthesis assuming that the gauge coupling constants of the fundamental interactions may vary. We analyze the dependence of the nucleon masses, nuclear binding energies and cross sections involved in the calculation of the abundances with the fundamental constants assuming the chiral limit of QCD. The abundances of light elements as a function of the fundamental constants are obtained. Finally, using the observational data of $\De$, $\Het$, $\He$ and $\Li$ we estimate constraints on the variation of the fundamental constants between the primordial nucleosynthesis and the present. All observational abundances and the WMAP estimate of the baryon density, can be fitted to the theoretical predictions with varying coupling constants. The possible systematic errors in the observational data, precludes from stronger conclusions.

astro-ph↗
arXiv2004

Causality and Sound Speed for General Scalar Field Models, including w < -1, tachyonic, phantom, k-essence and curvature corrections

The result from the SN1a projects suggest that the dark energy can be represented by a fluid with w<-1. However, it is commonly argued that a fluid with |w|>1 contradicts causality. Here, we will show that a fluid with |w|>1 does not contradict causality if $w$ is not constant. Scalar field are the most promising candidates for describing the dark energy and they do not have a constant equation of state parameter w. Scalar potentials may lead to regions where w is larger or smaller than one and even regions where the group velocity $d p/dρ$ diverges. We study the evolution of scalar field perturbations and we show that the "sound speed" is always smaller than the speed of light independently of the value of w=p/ρor d p/dρ. In general, it is neither the phase velocity nor the group velocity that gives the "sound speed". In the analysis we include the special cases of $|w|>1$, tachyonic, phantom, k-essence scalar fields and curvature corrections. Our results show that scalar fields do not contradict causality as long as there is dispersion.

astro-ph↗
arXiv2003

Limits on charge non-conservation from possible seasonal variations of the solar neutrino experiments

Variable speed of light (VSL) theories generically lead to large violations of charge conservation that can be written in terms of a dimensionless parameter $λ$. It is shown that the motion of the Earth with respect to the Sun could lead to a seasonal variation for the SAGE and GALLEX-GNO experiments and analyzing the reported counting rates for these experiments, a very stringent bound $λ\le 2 \times 10^{-19} $ is obtained, some $10^9$ times smaller than previous ones. Furthermore, a bound on the lifetime of the $\null^{71}{\rm Ga} \to \null^{71} {\rm Ge}$ charge-nonconserving decay in VSL theories is found as: $ τ_{\rm CNC} \ge 1.4 \times 10^{27} {\rm years}$. Similarly a new upper limit for the ratio of the charge-nonconserving to the normal weak decay of the neutron in VSL theories is obtained: $Γ(n \to p + ν_e + \barν_e) /Γ(n \to p + e + \barν_e) \le 2 \times 10^{-27}$.

astro-ph↗
arXiv2002

New Observational Bounds to Quantum Gravity Signals

We consider a new set of effects arising from the quantum gravity corrections to the propagation of fields, associated with fluctuations of the spacetime geometry. Using already existing experimental data, we can put bounds on these effects that are more stringent by several orders of magnitude than those expected to be obtained in astrophysical observations. In fact these results can be already interpreted as questioning the whole scenario of linear (in $l_P$) corrections to the dispersion relations for free fields in Lorentz violating theories.

gr-qc↗
arXiv2001

Testing theories that predict time variation of fundamental constants

We consider astronomical and local bounds on time variation of fundamental constants to test some generic Kaluza-Klein-like models and some particular cases of Beckenstein theory. Bounds on the free parameters of the different theories are obtained. Furthermore, we find that none of the proposed models, is able to explain recent results [Webb99,Webb00] claiming an observed variation of the fine structure constant from quasar absorption systems at redshifts $0.5<z<3$.

astro-ph↗
arXiv2001

Charge conservation and Equivalence principle

The $THεμ$ formalism was developed to study nonmetric theories of gravitation. In this letter we show that theories that violate Local Lorentz Invariance (LLI) or Local Position Invariance (LPI) also violate charge conservation. Using upper bounds on this violation we can put very stringent limits to violations of Einstein Equivalence Principle (EEP). These limits, in turn, severely restrict string-based models of low energy physics.

gr-qc↗
arXiv2001

Charge conservation and time-varying speed of light

It has been recently claimed that cosmologies with time dependent speed of light might solve some of the problems of the standard cosmological scenario, as well as inflationary scenarios. In this letter we show that most of these models, when analyzed in a consistent way, lead to large violations of charge conservation. Thus, they are severly constrained by experiment, including those where $c$ is a power of the scale factor and those whose source term is the trace of the energy-momentum tensor. In addition, early Universe scenarios with a sudden change of $c$ related to baryogenesis are discarded.

astro-ph↗