arXiv subjects

John Morales

Publications and source records attributed to John Morales.

At least 19 recordsLinked to original sources

arXiv2019

Jo: The Smart Journal

We introduce Jo, a mobile application that attempts to improve user's well-being. Jo is a journaling application--users log their important moments via short texts and optionally an attached photo. Unlike a static journal, Jo analyzes these moments and helps users take action towards increased well-being. For example, Jo annotates each moment with a set of values (e.g., family, socialization, mindfulness), thereby giving the user insights about the balance in their lives. In addition, Jo helps the user create reminders that enable them to create additional happy moments. We describe the results of fielding Jo in a study of 39 participants. The results illustrate the promise of a journaling application that provides personalized feedback, and points at further research.

cs.HC↗

arXiv2019

Voyageur: An Experiential Travel Search Engine

We describe Voyageur, which is an application of experiential search to the domain of travel. Unlike traditional search engines for online services, experiential search focuses on the experiential aspects of the service under consideration. In particular, Voyageur needs to handle queries for subjective aspects of the service (e.g., quiet hotel, friendly staff) and combine these with objective attributes, such as price and location. Voyageur also highlights interesting facts and tips about the services the user is considering to provide them with further insights into their choices.

cs.DB↗

arXiv2017

Free Energy of a Large-$N$ Pion Gas and Chiral Symmetry Restoration

We study thermal properties of a large-N massless pion gas using a low-energy QCD approach given by an $O(N +1)/O(N)$ Nonlinear Sigma Model. We build diagrammatically the associated finite free energy to $O(TM^{3})$ in the pion mass expansion through an effective vertex that considers all the contributions coming from closed diagrams. Subsequently, we calculate finite order parameters such as the quark condensate and its respective derivative, i.e., the scalar susceptibility, in the chiral limit, along with their associated critical exponents. These results are compared with our previous unitarized scattering analyses for the chiral transition universality class, thus showing a reasonable agreement both with lattice simulations and these resonant studies.

hep-ph↗

arXiv2017

Neutrino self-energy with new physics effects in an external magnetic field

We compute the magnetic dipole moment (MDM) for massive flavor neutrinos using the neutrino self-energy in a magnetized media. The framework to incorporate neutrino masses is one minimal extension of the Standard Model in which neutrinos are Dirac particles and their masses coming from tiny Yukawa couplings from a second Higgs doublet with a small vacuum expectation value. The computations are carried out by using proper time formalism in the weak field approximation $eB<<m_{e}^{2}$ and assuming normal hierarchy for neutrino masses and sweeping the charged Higgs mass. For $ν_τ$, analyses in the neutrino specific scenario indicate magnetic dipole moments greater than the values obtained to the MDM in the SM (with and without magnetic fields) and other flavor conserving models. This fact leading a higher proximity with experimental bounds and so on it is possible to get stronger exclusion limits over new physics parameter space.

hep-ph↗

arXiv2016

Chiral Symmetry Restoration for the large-$N$ pion gas

We analyze chiral restoration within the $O(N+1)/O(N)$ Non-Linear Sigma Model for large $N$ as an effective theory for low-energy QCD at finite temperature $T$. The free energy is constructed diagramatically to ${\cal O}(TM^3)$ in the pion mass expansion, which allows to derive the quark condensate and the scalar susceptibility in the chiral limit. At this order, we do not have to deal with renormalization, neither from divergences from mass tadpoles nor from those of higher order loop contributions. Our results for the critical behaviour are consistent with expectations from lattice analysis and with previous works where the susceptibility is saturated by the thermal $f_0(500)$ pole.

hep-ph↗

arXiv2016

Chiral Symmetry restoration from the hadronic regime

We discuss recent advances on QCD chiral symmetry restoration at finite temperature, within the theoretical framework of Effective Theories. $U(3)$ Ward Identities are derived between pseudoscalar susceptibilities and quark condensates, allowing to explain the behaviour of lattice meson screening masses. Unitarized interactions and the generated $f_0(500)$ thermal state are showed to play an essential role in the description of the transition through the scalar susceptibility

hep-ph↗

arXiv2016

Study of vacuum behavior for inert models with discrete $Z_{2}$-like and abelian $U(1)$ symmetries

We study the vacuum behavior at one loop level in extended Higgs sectors with two doublets (2HDM), where $U(1)$ and $Z_{2}$ symmetries are considered to protect the $CP$ symmetry in the Higgs potential and to avoid Flavor Changing Neutral Currents at tree level in the Yukawa sector. In the Inert Higgs Model case, a detailed comparison is made between both models by using the energy evolution of couplings, which should satisfy energy scale dependent relations deduced for minima and stationary points of the Higgs potential at tree level. Besides, perturbative unitarity constraints at tree level are considered to generate the allowed parameter space compatible with perturbativity (absence of Landau poles). Our studies illustrate exclusion regions for Higgs masses and other combinations of couplings in the scalar sector, in particular for splittings of mass square for neutral scalars $A^{0}$ and $H^{0}$, as well as the difference between the sum of these and the charged Higgs mass square. From the vacuum stability for inert-2HDM at the tree and one loop levels, analyses lead us to find out new hierarchical structures for scalar masses. To complete vacuum studies on the Inert model, and based on reparameterization invariance of the Higgs potential, we compute original discriminants that allow ensuring the presence of a global electroweak minimum at tree level. Moreover, the behavior in high energy scales drives out analyzing criticality phenomena for the additional parameters of extended Higgs sectors. Finally, and using the consistency with the electroweak precision analyses of oblique parameters, we describe several implications from different regimes of the inert model on charged and pseudoscalar Higgs searches.

hep-ph↗

arXiv2016

Phenomenology of the new physics coming from 2HDMs to the neutrino magnetic dipole moment

In several frameworks for leptons-sectors of two Higgs doublet models, we calculate the magnetic dipole moment for the different flavor types of neutrino. Computations are carried out by assuming a normal hierarchy for neutrino masses, and analyzing the process $ν\rightarrow νγ$ with a charged Higgs boson into the loop. The analysis was performed by sweeping the charged Higgs mass and taking into account the experimental constraints for relevant parameters in Two Higgs Doublet Models with and without flavor changing neutral currents; obtaining magnetic dipole moments close to the experimental thresholds for tau neutrinos in type II and Lepton-specific cases. In the neutrino-specific scenario, the contribution of new physics could be sizeable to the current measurement for flavor magnetic dipole moment. This fact leads to excluding possible zones in the parameter space of charged Higgs mass and vacuum expectation value of the second doublet.

hep-ph↗

arXiv2016

Phenomenological aspects from vacuum stability and metastability in models with soft breaking of a \texorpdfstring{$U\left( 1\right)$}{lg} global symmetry

We study the vacuum behavior of an extended Higgs sector with two doublets in a scenario with a softly broken \texorpdfstring{$U(1)$}{lg} global symmetry. The soft-violation term is introduced to avoid massless-axion particles arising when the global symmetry becomes spontaneously broken. This model has metastable states through the possible presence of multiple non-degenerate minima, which is unwanted from the phenomenological point of view if the metastable state is not long-lived enough. The analysis of this fact leads to find possible exclusion limits over parameter space of quartic couplings. Results improve the individual behavior of initial conditions for renormalization group equations; also determining unstable zones for the effective Higgs potential at one loop level. Besides vacuum stability analyses, the influence of absence of charge violation minima is considered as a limiting case excluding zones in the parameter space. Extremal cases for the model as well as criticality phenomena are discussed with the aid of relation among Higgs masses or splittings among them. From vacuum behavior and LHC results, phenomenological aspects in the searching of charged and heavier Higgs bosons are considered to evaluate the scalar alignment regimen of the two Higgs doublet model.

hep-ph↗

arXiv2016

Large-$N$ pion scattering at finite temperature: the $f_0(500)$ and chiral restoration

We consider the $O(N+1)/O(N)$ Non-Linear Sigma Model for large $N$ as an effective theory for low-energy QCD at finite temperature $T$, in the chiral limit. At $T=0$ this formulation provides a good description of scattering data in the scalar channel and generates dynamically the $f_0(500)$ pole, the pole position lying within experimental determinations. Previous $T=0$ results with this model are updated using newer analysis of pion scattering data. We calculate the pion scattering amplitude at finite $T$ and show that it satisfies exactly thermal unitarity, which had been assumed but not formally proven in previous works. We discuss the main differences with the $T=0$ result and we show that one can define a proper renormalization scheme with $T=0$ counterterms such that the renormalized amplitude can be chosen to depend only on a few parameters. Next, we analyze the behaviour of the $f_0(500)$ pole at finite $T$, which is consistent with chiral symmetry restoration when the scalar susceptibility is saturated by the $f_0(500)$ state, in a second-order transition scenario and in accordance with lattice and theoretical analysis.

hep-ph↗

arXiv2016

Large-$N$ Pion Scattering, Finite-Temperature Effects and the Relationship of the $f_{0}(500)$ with Chiral Symmetry Restoration

In this work, we review how the mass and the width of the $f_{0}(500)$ pole behave in a regime where temperature is below the critical chiral transition value. This is attained by considering a large-$N$ $O(N + 1)/O(N)$ invariant Non-Linear Sigma Model (NLSM) such that we can study the dynamical generation of a $f_{0}(500)$ resonance. Introducing thermal effects via the imaginary time formalism allows us to study the behavior of the pole and relate it to chiral restoration.

hep-ph↗

arXiv2015

Constraints on neutrino masses coming from magnetic dipole moments in a two Higgs doublet model type I and II

In the framework of a two Higgs doublet model type I and type II, we calculate limits on neutrino masses for the different types of neutrinos, by using the experimental bounds on their magnetic dipole moments. This is carried out by analyzing diagrams of Cherenkov neutrino decays with a charged Higgs into the loop, coming from the two Higgs doublet model (2HDM). Such constraints are translated into allowed regions in the free parameters of the models, for each neutrino flavor. The analysis was performed by sweeping the charged Higgs mass between (100-900)GeV and taking into account the experimental constraints for $\tanβ$ in the 2HDM type I and II, obtaining contributions close to the experimental thresholds for muon and tau neutrinos, while for electron neutrino the relevant contribution comes from standard model and keeps out of the reach of forthcoming experiments.

hep-ph↗

arXiv2013

Unitarity constraints for Yukawa couplings in the two Higgs doublet model type III

Unitarity constraints for Yukawa couplings are considered in the Two Higgs Doublet Model type III, by using a general expansion in partial waves for fermionic scattering processes. Constraints over general Flavor Changing Neutral Currents are found from that systematic, such bounds compete with those coming from Lagrangian perturbativity requirement but are weaker than those imposed from phenomenological processes and precision tests. Nevertheless, for bounds based on unitarity the number of assumptions is the lowest among phenomenological and theoretical limits. Indeed, these new theoretical constraints are independent of scalar masses or mixing angles for this extended Higgs sector, making them less model dependent.

hep-ph↗

arXiv2012

Energy operator for non-relativistic and relativistic quantum mechanics revisited

Hamiltonian operators are gauge dependent. For overcome this difficulty we reexamined the effect of a gauge transformation on Schrödinger and Dirac equations. We show that the gauge invariance of the operator $H-i\hbar\frac{\partial}{\partial t}$ provides a way to find the energy operator from first principles. In particular, when the system has stationary states the energy operator can be identified without ambiguities for non-relativistic and relativistic quantum mechanics. Finally, we examine other approaches finding that in the case in which the electromagnetic field is time independent, the energy operator obtained here is the same as one recently proposed by Chen et al. [1].

math-ph↗

arXiv2005

Higgs boson decay in the large N limit

The Equivalence Theorem is commonly used to calculate perturbatively amplitudes involving gauge bosons at energy scales higher than gauge boson masses. However, when the scalar sector is strongly interacting the theory is non-perturbative. We show that the Equivalence Theorem holds in the large N limit at next-to-leading order by calculating the decay widths h -> W^{+}W^{-} and h->π^{+}π^{-}. We also show, in the same scheme of calculations, that unitarity is fulfilled for the process h->π^{+}π^{-}.

hep-ph↗

arXiv2001

Rest masses of elementary particles as effective masses at zero temperature

We introduce a new approach to generate dinamically the masses of elementary particles in the $SU(3)_C \times SU(2)_L \times U(1)_Y$ Standard Model without Higgs Sector (SMWHS). We start from the assumption that rest masses correspond to the effective masses of particles in an elementary quantum fluid at zero temperature. These effective masses are obtained through radiative corrections, at one-loop order, in the context of the real time formalism of quantum field theory at finite temperature and density. The quantum fluid is described in structure and dynamics by the SMWHS and it is characterized by non-vanishing chemical potentials associated to the different fermion flavour species. Starting from the experimental mass values for quarks and leptons, taking the top quark mass as $m_t = 172.916$ GeV, we can compute, as an evidence of the consistency of our approach, the experimental central mass values for the $W^{\pm}$ and $Z^0$ gauge bosons. Subsequently we introduce in the SMWHS a massless scalar field leading to Yukawa coupling terms in the Lagrangian density. For this case we can also compute the experimental mass central values of the $W^{\pm}$ and $Z^0$ gauge bosons using a top quark mass value in the range 169.2 GeV $< m_{t} < 178.6$ GeV; this range for the top quark mass implies that the scalar boson mass must be in the range $0 < M_{H} < 152$ GeV.

hep-ph↗

arXiv2000

Can large fermion chemical potentials suppress the electroweak phase transition ?

We calculate the critical temperature $(T_c$) of the electroweak phase transition in the minimal standard model considering simultaneously temperature ($T$) and fermion chemical potential ($μ_f$) effects over the effective potential. The calculation is performed in the one-loop approximation to the effective potential at non-zero temperature using the real time formalism of the thermal field theory. We show that it exists a fermion chemical potential critical value ($μ_f^c$) for which the Higgs boson condensate vanishes at T=0. If $T$ and $μ_f$ effects are considered simultaneously, it is shown that for $μ_f \geq μ_f^c$ then $T_c^2 \leq 0$, implying that the electroweak phase transition might not take place.

hep-ph↗

arXiv1999

Dispersion relations at finite temperature and density for nucleons and pions

We calculate the nucleonic and pionic dispersion relations at finite temperature T and non-vanishing chemical potentials $(μ_f)$ in the context of an effective chiral theory that describes the strong and electromagnetic interactions for nucleons and pions. The dispersion relations are calculated in the broken chiral symmetry phase, where the nucleons are massive and pions are taken as massless. The calculation is performed at lowest order in the energy expansion, working in the framework of the real time formalism of thermal field theory in the Feynman gauge. These one-loop dispersion relations are obtained at leading order with respect to T and $μ_f$. We also evaluate the effective masses of the quasi-nucleon and quasi-pion excitations in thermal and chemical conditions as the ones of a neutron star.

hep-ph↗