scholarly journals Minimal theory of massive gravity and constraints on the graviton mass

2021 ◽  
Vol 2021 (12) ◽  
pp. 011
Author(s):  
Antonio De Felice ◽  
Shinji Mukohyama ◽  
Masroor C. Pookkillath

Abstract The Minimal theory of Massive Gravity (MTMG) is endowed non-linearly with only two tensor modes in the gravity sector which acquire a non-zero mass. On a homogeneous and isotropic background the theory is known to possess two branches: the self-accelerating branch with a phenomenology in cosmology which, except for the mass of the tensor modes, exactly matches the one of ΛCDM; and the normal branch which instead shows deviation from General Relativity in terms of both background and linear perturbations dynamics. For the latter branch we study using several early and late times data sets the constraints on today's value of the graviton mass μ0, finding that (μ0/H 0)2 = 0.119-0.098 +0.12 at 68% CL, which in turn gives an upper bound at 95% CL as μ0 < 8.4 × 10-34 eV. This corresponds to the strongest bound on the mass of the graviton for the normal branch of MTMG.

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Hongsheng Zhang ◽  
Yang Huang

Abstract Spherical gravitational wave is strictly forbidden in vacuum space in frame of general relativity by the Birkhoff theorem. We prove that spherical gravitational waves do exist in non-linear massive gravity, and find the exact solution with a special singular reference metric. Further more, we find exact gravitational wave solution with a singular string by meticulous studies of familiar equation, in which the horizon becomes non-compact. We analyze the properties of the congruence of graviton rays of these wave solution. We clarify subtle points of dispersion relation, velocity and mass of graviton in massive gravity with linear perturbations. We find that the graviton ray can be null in massive gravity by considering full back reaction of the massive gravitational waves to the metric. We demonstrate that massive gravity has deep and fundamental discrepancy from general relativity, for whatever a tiny mass of the graviton.


2011 ◽  
Vol 20 (14) ◽  
pp. 2803-2807 ◽  
Author(s):  
KAZUYA KOYAMA ◽  
GUSTAVO NIZ ◽  
GIANMASSIMO TASINATO

In this essay, we address two long-standing problems of massive gravity: The ghost mode found by Boulware and Deser, and the incompatibility with General Relativity in the massless limit, better known as the vDVZ discontinuity. We present a recent candidate for a ghost-free theory, and show how Einstein's gravity is recovered within a certain macroscopic radius from a mass source, via the Vainshtein mechanism. We also exhibit an exact solution which could account for the late time acceleration of the Universe by means of a small graviton mass.


Author(s):  
Stefan Krause ◽  
Markus Appel

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.


Author(s):  
Mark Byers

This concluding chapter charts the continuing significance of the early postwar moment in Olson’s later work, particularly The Maximus Poems. The philosophical and political concerns of the American avant-garde between 1946 and 1951 play out across The Maximus Poems just as they inform later American art practices. The search of the early postwar American independent left for a source of political action rooted in the embodied individual is seen, on the one hand, to have been personified in the figure of Maximus. At the same time, Maximus’s radical ‘practice of the self’ charts a sophisticated alternative to the Enlightenment humanist subject widely critiqued in the United States in the immediate postwar period.


Author(s):  
Stacy Wolf

This chapter examines the eight female characters inCompany, what they do in the musical, and how they function in the show’s dramaturgy, and argues that they elicit the quintessential challenge of analyzing musical theater from a feminist perspective. On the one hand, the women tend to be stereotypically, even msogynistically portrayed. On the other hand, each character offers the actor a tremendous performance opportunity in portraying a complicated psychology, primarily communicated through richly expressive music and sophisticated lyrics. In this groundbreaking 1970 ensemble musical about a bachelor’s encounters with five married couples and three girlfriends, Sondheim’s female characters occupy a striking range of types within one show. From the bitter, acerbic, thrice-married Joanne to the reluctant bride-to-be Amy, and from the self-described “dumb” “stewardess” April to the free-spirited Marta,Company’s eight women are distillations of femininity, precisely sketched in the short, singular scenes in which they appear.


2020 ◽  
pp. 1-17
Author(s):  
Francisco Javier Balea-Fernandez ◽  
Beatriz Martinez-Vega ◽  
Samuel Ortega ◽  
Himar Fabelo ◽  
Raquel Leon ◽  
...  

Background: Sociodemographic data indicate the progressive increase in life expectancy and the prevalence of Alzheimer’s disease (AD). AD is raised as one of the greatest public health problems. Its etiology is twofold: on the one hand, non-modifiable factors and on the other, modifiable. Objective: This study aims to develop a processing framework based on machine learning (ML) and optimization algorithms to study sociodemographic, clinical, and analytical variables, selecting the best combination among them for an accurate discrimination between controls and subjects with major neurocognitive disorder (MNCD). Methods: This research is based on an observational-analytical design. Two research groups were established: MNCD group (n = 46) and control group (n = 38). ML and optimization algorithms were employed to automatically diagnose MNCD. Results: Twelve out of 37 variables were identified in the validation set as the most relevant for MNCD diagnosis. Sensitivity of 100%and specificity of 71%were achieved using a Random Forest classifier. Conclusion: ML is a potential tool for automatic prediction of MNCD which can be applied to relatively small preclinical and clinical data sets. These results can be interpreted to support the influence of the environment on the development of AD.


2018 ◽  
Vol 19 (2) ◽  
pp. 421-450 ◽  
Author(s):  
Stephen Scully

Let $q$ be an anisotropic quadratic form defined over a general field $F$. In this article, we formulate a new upper bound for the isotropy index of $q$ after scalar extension to the function field of an arbitrary quadric. On the one hand, this bound offers a refinement of an important bound established in earlier work of Karpenko–Merkurjev and Totaro; on the other hand, it is a direct generalization of Karpenko’s theorem on the possible values of the first higher isotropy index. We prove its validity in two key cases: (i) the case where $\text{char}(F)\neq 2$, and (ii) the case where $\text{char}(F)=2$ and $q$ is quasilinear (i.e., diagonalizable). The two cases are treated separately using completely different approaches, the first being algebraic–geometric, and the second being purely algebraic.


2007 ◽  
Vol 3 (S248) ◽  
pp. 290-291 ◽  
Author(s):  
A. Vecchiato ◽  
M. G. Lattanzi ◽  
M. Gai ◽  
R. Morbidelli

AbstractGAME (Gamma Astrometric Measurement Experiment) is a concept for an experiment whose goal is to measure from space the γ parameter of the Parameterized Post-Newtonian formalism, by means of a satellite orbiting at 1 AU from the Sun and looking as close as possible to its limb. This technique resembles the one used during the solar eclipse of 1919, when Dyson, Eddington and collaborators measured for the first time the gravitational bending of light. Simple estimations suggest that, possibly within the budget of a small mission, one could reach the 10−6level of accuracy with ~106observations of relatively bright stars at about 2° apart from the Sun. Further simulations show that this result could be reached with only 20 days of measurements on stars ofV≤ 17 uniformly distributed. A quick look at real star densities suggests that this result could be greatly improved by observing particularly crowded regions near the galactic center.


2005 ◽  
Vol 15 (01n02) ◽  
pp. 101-110 ◽  
Author(s):  
TIMO SIMILÄ ◽  
SAMPSA LAINE

Practical data analysis often encounters data sets with both relevant and useless variables. Supervised variable selection is the task of selecting the relevant variables based on some predefined criterion. We propose a robust method for this task. The user manually selects a set of target variables and trains a Self-Organizing Map with these data. This sets a criterion to variable selection and is an illustrative description of the user's problem, even for multivariate target data. The user also defines another set of variables that are potentially related to the problem. Our method returns a subset of these variables, which best corresponds to the description provided by the Self-Organizing Map and, thus, agrees with the user's understanding about the problem. The method is conceptually simple and, based on experiments, allows an accessible approach to supervised variable selection.


Author(s):  
Judson B. Murray

Confucian mysticism is a subfield in academic areas of study including Chinese thought, Chinese religions, Confucian studies, and comparative mysticism. Important topics examined in this subfield include, first, a view of the human self that is fundamentally relational, both in an interpersonal sense and because Confucians presuppose various correlations and an integration between, on the one hand, the matter–energy, capacities, processes, and activities comprising the self and, on the other, the elements, forces, patterns, and processes of the world it inhabits. One paradigmatic way Confucians conceptualize the interrelation between the self and the cosmos is their idea and ideal of the “unity of Heaven and humanity.” The Confucian mystical self, provided failings such as unbalanced emotions, selfish desires, and self-centeredness are effectively curtailed, contributes vitally to, because of its profound reverence for life, the generative and life-sustaining process of change that pervades and animates the cosmos. Second, practitioners use various techniques of religious praxis in combination to form multifaceted training regimens aimed at self-cultivation and self-transformation. Examples include a form of meditation called “quiet-sitting,” rituals, textual study, “investigating things,” self-examination and self-monitoring, filial piety, and “reverent attentiveness.” Third, training in these practices can achieve the different mystical aims, experiences, and transformations they seek, all of which relate to the overarching ideal of the unity of Heaven and humanity. These objectives, broadly speaking, include self-understanding, accurately grasping the “principles” of things and affairs, effortless moral virtuosity, “forming one body with all things” (and other types of Confucian mystical union), and exemplifying “sincerity.” Accomplishing them collapses the conventional divide separating several specious dichotomies, such as thought and action, self and other, humankind and nature, internal and external, the subjective and the objective, and moral ought and is. Fourth, the influence that precedent and tradition exert in Confucianism has prompted scholars to devote attention both to notable continuities and to intriguing innovations in comparing ancient mystical ideas, practices, experiences, and aims to later expressions and elaborations of them. At present, much of the scholarship on Confucian mysticism contributes to efforts attempting to provide rich and nuanced analyses of the tradition’s core doctrines, practices, experiences, and ethical and religious aims, by viewing these subjects through the lens of Confucianism’s mystical and spiritual dimensions. Less scholarly attention has been devoted to identifying and explicating the possible contributions that studying Confucian mysticism can make to the scholarship on theories of mysticism and comparative mysticism. Scholars of mysticism have not yet availed themselves of the wealth of data, the possible additional perspectives on contested issues, and the new trajectories for future research that Confucianism offers to these fields. Also, few studies employ the definitions, categories, and theories that have been developed in the contemporary study of mysticism as a methodology for studying Confucian mysticism.


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