Invisible Sector Research Articles

Dark radiation from the primordial thermal bath in momentum space

Motivated by the stunning projections for future CMB surveys, we evaluate the amount of dark radiation produced in the early Universe by two-body decays or binary scatterings with thermal bath particles via a rigorous analysis in momentum space. We track the evolution of the dark radiation phase space distribution, and we use the asymptotic solution to evaluate the amount of additional relativistic energy density parameterized in terms of an effective number of additional neutrino species ΔN eff. Our approach allows for studying light particles that never reach equilibrium across cosmic history, and to scrutinize the physics of the decoupling when they thermalize instead. We incorporate quantum statistical effects for all the particles involved in the production processes, and we account for the energy exchanged between the visible and invisible sectors. Non-instantaneous decoupling is responsible for spectral distortions in the final distributions, and we quantify how they translate into the corresponding value for ΔN eff. Finally, we undertake a comprehensive comparison between our exact results and approximated methods commonly employed in the existing literature. Remarkably, we find that the difference can be larger than the experimental sensitivity of future observations, justifying the need for a rigorous analysis in momentum space.

Absorptive effects and classical black hole scattering

We describe an approach to incorporating the physical effects of the absorption of energy by the event horizon of black holes in the scattering amplitudes based post-Minkowskian, point-particle effective description. Absorptive dynamics are incorporated in a model-independent way by coupling the usual point-particle description to an invisible sector of gapless internal degrees-of-freedom. The leading order dynamics of this sector are encoded in the low-energy expansion of a spectral density function obtained by matching an absorption cross section in the ultraviolet description. This information is then recycled using the scattering amplitudes based Kosower-Maybee-O’Connell in-in formalism to calculate the leading absorptive contribution to the impulse and change in rest mass of a Schwarzschild black hole scattering with a second compact body sourcing a massless scalar, electromagnetic or gravitational field. The results obtained are in complete agreement with previous worldline Schwinger-Keldysh calculations and provide an alternative on-shell scattering amplitudes approach to incorporating horizon absorption effects in the gravitational two-body problem.

Safety Trade-Offs in Home Care During COVID-19: A Mixed Methods Study Capturing the Perspective of Frontline Workers

Background: Home care workers help older individuals and those with disabilities with a variety of functional tasks. Despite their core role providing essential care to vulnerable populations, home care workers are often an invisible sector of the healthcare workforce. The transmission of COVID-19 and the nature of home care work raise several questions about the overall safety of these workers during the pandemic. Objective: To examine the experiences of home care workers during COVID-19, particularly their access to information about infection status, to testing, and to personal protective equipment (PPE); their understanding of guidelines; and trade-offs associated with protecting workers’ safety. Methods: A mixed methods study including qualitative analysis of guided discussion questions and quantitative analysis of multiple-choice survey questions was conducted. Eleven virtual focus groups in October and November 2020 involved 83 home care workers who care for clients/consumers in Massachusetts. Thirty-nine participants worked as personal care attendants (PCAs) employed directly by a consumer and 44 participants worked for an agency. Ninety percent self-identified as female and 54% had worked in home care for more than five years. Qualitative data was analyzed using thematic analysis, with identification of major and minor themes. Likert scale survey question data on perceptions of COVID-19 exposure, access to resources to prevent transmission, and perceptions of safety at work were dichotomized into agree or disagree. Results: PCAs and agency-employed home care workers were regularly faced with trade-offs between meeting client/consumer needs and protecting themselves from COVID-19 exposure. Twenty-five percent of participants reported serving a client/consumer who had COVID-19, 75% reported worrying about getting COVID-19 at work, and 29% reported thinking about stopping their work in home care. Despite a low pay structure, participants reported opting to risk exposure rather than to leave their clients/consumers without essential care. However, workers often lacked the resources (e.g., PPE, testing) to feel truly protected. This scarcity of resources combined with insufficient guidance and policies specific to home care settings led many workers to informally collaborate with clients/consumers to assess exposure risks and agree upon safety protocols. Focus group participants expressed uncertainty as to whether workers were truly empowered to ask for changes if conditions seemed unsafe. The burden of determining safety protocols was felt more strongly by PCAs who operate more independently than agency-employed workers who have supervisors to consult. Conclusions: Home care workers expressed deep commitment to continuing to care for their clients/consumers during COVID-19, but often had to operate with insufficient resources and under conditions that made their work environments feel unsafe. Their ability to identify exposure risks and make decisions on how to protect themselves often hinged on a transparent and trusting relationship with their clients/consumers. These relationships were particularly important for PCAs who did not have access to safety guidance from a home care agency.

Invisible QCD as Dark Energy

We account for the late time acceleration of the Universe by extending the Quantum Chromodynamics (QCD) color to a S U ( 3 ) invisible sector (IQCD). If the Invisible Chiral symmetry is broken in the early universe, a condensate of dark pions (dpions) and dark gluons (dgluons) forms. The condensate naturally forms due to strong dynamics similar to the Nambu–Jona-Lasinio mechanism. As the Universe evolves from early times to present times the interaction energy between the dgluon and dpion condensate dominates with a negative pressure equation of state and causes late time acceleration. We conclude with a stability analysis of the coupled perturbations of the dark pions and dark gluons.

Cosmological dark matter in a conformal model

We study the collider, astrophysical and cosmological constraints on the dark matter sector of a conformal model within the framework of both the freeze out as well as the freeze in mechanism. The model has a dark sector with strong self interactions. This sector couples weakly with the Standard Model (SM) particles via a scalar messenger. The lightest dark sector particle is a pion-like fermion anti-fermion bound state. We find that the model successfully satisfies the constraints coming from the Higgs decay to the visible as well as the invisible sector. We have used the results of the dark matter direct detection experiments, such as, XENON1T in order to impose bounds on the parameters of the model. The model satisfies the indirect detection constraints of gamma ray from the galactic center and Dwarf spheroidal galaxies. We also determine the parameter range for which it satisfies the astrophysical constraints on the dark matter self coupling.

La Comunicación Intercultural en la Educación Superior Intercultural, desde los Pueblos Indígenas y Afrodescendientes

El presente artículo presenta dos experiencias particulares del camino recorrido de la Red de Universidades Indígenas Interculturales y Comunitarias de Abya Yala, RUIICAY, y la Universidad de las Regiones Autónomas de la Costa Caribe Nicaragüense, URACCAN, vista desde 2 procesos: implementación del proyecto de vinculación de la comunicación intercultural y la experiencia de evaluación de las universidades en Nicaragua, en las que se evidencian ciertas características de la comunicación intercultural. El artículo pretende evidenciar buenas prácticas que, aporten a la sistematización de procesos que contribuyen a la garantía de la educación superior de sectores históricamente invisibilizados, y que no han tenido la posibilidad de compartir, practicar y revitalizar sus tradiciones y costumbres desde la colectividad.

Occupational health and safety: educational intervention for cleaning workers in research sectors

To evaluate the results of educational interven- tion on health and safety regarding principles of biosafety in cleaning workers of a health institution. Using concurrent mixed methods, we evaluated a total of 31 workers on their knowledge, attitudes, and practices of biosafety and risk perception. We conducted baseline measurements and two follow-ups. Fractional logistic regression models were fitted with study stage as covariate. Additional models included interactions of study stage with key workers characteristics. Thematic qualitative analysis and triangulation was developed. The knowledge (+33.3 points, scale 0-100), attitudes (+10.6), and practices (+23.5) increased significantly in the first follow-up; knowledge de- creased in the second follow-up (p<0.001). The qualitative findings revealed an improvement in risk prevention attitudes and practices, framed by experiences of vulnerability, stigma, and discrimination. The study provides key elements for biosafety research related to vulnerable groups and it is effective in promoting the health of a disadvantaged and invisible sector.

Light (and darkness) from a light hidden Higgs

We examine light diphoton signals from extended Higgs sectors possessing (approximate) fermiophobia with Standard Model (SM) fermions as well as custodial symmetry. This class of Higgs sectors can be realized in various beyond the SM scenarios and is able to evade many experimental limits, even at light masses, which are otherwise strongly constraining. Below the WW threshold, the most robust probes of the neutral component are di and multi-photon searches. Utilizing the dominant Drell-Yan Higgs pair production mechanism and combining it with updated LHC diphoton data, we derive robust upper bounds on the allowed branching ratio for masses between 45 − 160 GeV. Furthermore, masses ≲ 110 GeV are ruled out if the coupling to photons is dominated by W boson loops. We then examine two simple ways to evade these bounds via cancellations between different loop contributions or by introducing decays into an invisible sector. This also opens up the possibility of future LHC diphoton signals from a light hidden Higgs sector. As explicit realizations, we consider the Georgi-Machacek (GM) and Supersymmetric GM (SGM) models which contain custodial (degenerate) Higgs bosons with suppressed couplings to SM fermions and, in the SGM model, a (neutralino) LSP. We also breifly examine the recent ∼ 3σ CMS diphoton excess at ∼ 95 GeV.

Genuine and effective actions, the Master Equation and Suppressed SUSY

Genuine theories are defined to be those governed by a Master Equation. All other theories are defined to be Effective Theories. It is straightforward to integrate heavy particles out of a Genuine Theory to get an Effective Theory, but putting together a Genuine Theory takes years. The Minimal Supersymmetric Standard Model is an Effective Theory, which arises because of the hypothesis of an invisible sector where spontaneous breaking of Supersymmetry (SUSY) occurs. Suppressed SUSY allows us to construct a Genuine Theory for SUSY, without the need for spontaneous breaking of SUSY.

Acercamiento a las mediaciones en la producción simbólica pública de Las Villas en la medianía del siglo xx

The examination from a hermeneutic, systemic, and reflective view of the public symbolic production of island society in Cuba, during the Republican period, 40 and 50 decades of the 20th century, accuses the relevance of the historiography of communication as an interdisciplinary construct, able to activate the procedural relations between the economic, legal, political, and cultural dimensions that distinguished the period, its actors, structures and supports, as well as the macro and micro mediations that affected the articulations between the social system and the communication public system, at the scale of what happens in local and regional societies. The context of the Constitution of 1940, of a bourgeois-democratic nature, only impacts the sphere of civil rights, the participation of historically invisible sectors, as well as the empowerment of commercial sectors, with a Spanish and immigrant presence, and a distinctive public and plural life that tended to reinforce an endogenous regionalist vision.This article, which responds to an ongoing PhD study, seeks inter- and transdisciplinary key, and from the logical-historical, diachronic analysis, to give emphasis to the documentary research, bibliography, the criterion of experts and the analysis of qualitative content, for an unprecedented conceptual and categorical construction in the field of the history of communication in Cuba.

Temporal and spatial strategies in an active place avoidance task on Carousel: a study of effects of stability of arena rotation speed in rats.

The active place avoidance task is a dry-arena task used to assess spatial navigation and memory in rodents. In this task, a subject is put on a rotating circular arena and avoids an invisible sector that is stable in relation to the room. Rotation of the arena means that the subject’s avoidance must be active, otherwise the subject will be moved in the to-be-avoided sector by the rotation of the arena and a slight electric shock will be administered. The present experiment explored the effect of variable arena rotation speed on the ability to avoid the to-be-avoided sector. Subjects in a group with variable arena rotation speed learned to avoid the sector with the same speed and attained the same avoidance ability as rats in a group with a stable arena rotation speed. Only a slight difference in preferred position within the room was found between the two groups. No difference was found between the two groups in the dark phase, where subjects could not use orientation cues in the room. Only one rat was able to learn the avoidance of the to-be-avoided sector in this phase. The results of the experiment suggest that idiothetic orientation and interval timing are not crucial for learning avoidance of the to-be-avoided sector. However, idiothetic orientation might be sufficient for avoiding the sector in the dark.

Gravi-weak unification and multiple-point principle

The problem of self-consistency of the unification of gravity and weak SU(2) interaction in a model that is invariant under the Spin(4, 4) group is studied. For this purpose, consequences of the multicritical-point principle, which admits the existence of two degenerate vacua in the Standard Model, are considered. Also, the existence of a visible and an invisible sector in our Universe is assumed.

Standard model and graviweak unification with (super)renormalizable gravity. Part I: Visible and invisible sectors of the universe

We develop a self-consistent Spin (4, 4)-invariant model of the unification of gravity with weak SU(2) gauge and Higgs fields in the visible and invisible sectors of our universe. We consider a general case of the graviweak unification, including the higher-derivative super-renormalizable theory of gravity, which is a unitary, asymptotically-free and perturbatively consistent theory of the quantum gravity.

The Universe in the Light of LHC

The Large Hadron Collider (LHC) provides data which give information on dark matter. In particular, measurements related to the Higgs sector lead to strong constraints on the invisible sector which are competitive with astrophysical limits. Some recent LHC results on dark matter coming from the Higgs sector in the Inert Doublet Model (IDM) are presented.

Reconstructing Higgs boson properties from the LHC and Tevatron data

Abstract We perform a phenomenological fit to all ATLAS, CMS, CDF and D0 Higgs boson data available after Moriond 2012. We allow all Higgs boson branching fractions, its couplings to standard model particles, as well as to an hypothetical invisible sector to vary freely, and determine their current favourite values. The standard model Higgs boson with a mass 125 GeV correctly predicts the average observed rate and provides an acceptable global fit to data. However, better fits are obtained by non-standard scenarios that reproduce anomalies in the present data (more γγ and less WW signals than expected) such as modified rates of loop processes or partial fermiophobia. We find that present data disfavours Higgs boson invisible decays. We consider implications for the standard model, for supersymmetric and fermiophobic Higgs bosons, for dark matter models, for warped extra-dimensions.

The abnormally weighting energy hypothesis: the missing link between dark matter anddark energy

We generalize tensor–scalar theories of gravitation by the introduction of an ‘abnormallyweighting’ type of energy. This theory of tensor–scalar anomalous gravity is based on arelaxation of the weak equivalence principle that is currently restricted to ordinary visiblematter only. As a consequence, the mechanism of convergence toward generalrelativity is modified and produces cosmic acceleration naturally as an inescapablegravitational feedback induced by the mass variation of some invisible sector. Thecosmological implications of this new theoretical framework are studied. From theHubble diagram cosmological test alone, this theory provides estimates of theamount of baryons and dark matter in the Universe that are consistent with theindependent cosmological tests of the cosmic microwave background and big bangnucleosynthesis. Cosmic coincidence is naturally achieved from an equally naturalassumption on the amplitude of the scalar coupling strength. Finally, from theadequacy for supernovae data, we derive a new intriguing relation between thespace–time dependences of the gravitational coupling and the dark matter mass,providing an example of a crucial constraint on microphysics from cosmology. Thisprovides glimpses of an enticing new symmetry between the visible and invisiblesectors, namely that the scalar charges of visible and invisible matter are exactlyopposite.

Nonminimal N=1 supergravity effective theories.

We address the problem of the minimization of the scalar potential with respect to the hidden field in the framework of N = 1 supergravity with a particular class of nonminimal scalar couplings which leads to flat potentials and thus a sliding gravitino mass. We show that a tree-level determination of m/sub 3/2/ is possible through an interplay of both visible and invisible sectors. Different types of effective theories are finally derived.