25 research outputs found
A novel approach to baryogenesis in gravity and its cosmological implications
No full textWe present an examination of the gravity model, in which the functional form is postulated and discuss its potential impact on cosmological dynamics and the phenomenon of gravitational baryogenesis. Combining observational insights from Hubble, BAO and phantom datasets, we conduct a comprehensive analysis to constrain the model\u27s parameters and determine the baryon-to-entropy ratio , providing valuable insights into the model\u27s performance and cosmological implications. In the context of baryogenesis and generalized gravitational baryogenesis, we show that setting results in a zero baryon-to-entropy ratio, which is physically implausible. Through a detailed examination of the dependence of on and , we demonstrate that our model predicts a baryon-to-entropy ratio that is both positive and consistent with the observational upper limit of for and appropriate of and with . The excellent agreement between our model\u27s predictions and the phantom dataset demonstrates the model\u27s capacity to accurately describe the physics of baryogenesis and its ability to reproduce the observed features of the cosmological data, showcasing its potential as a reliable tool for understanding the evolution of the Universe.20 pages, 7 figure
Qualitative stability analysis of cosmological parameters in
No full textWe analyze the cosmological solutions of f(T, B) gravity using dynamical system analysis where T is the torsion scalar and B be the boundary term scalar. In our work, we assume three specific cosmological models. For first model, we consider , where k and m are constants. For second model, we consider , for third model, we consider . We generate an autonomous system of differential equations for each models by introducing new dimensionless variables. To solve this system of equations, we use dynamical system analysis. We also investigate the critical points and their natures, stability conditions and their behaviors of Universe expansion. For first and second models, we get two stable critical points, while for third model we get one stable critical point. The phase plots of this system are analyzed in detail and study their geometrical interpretations also. For these three models, we evaluated density parameters such as , , and and deceleration parameter (q) and find their suitable range of the parameter for stability. For first model, we get and for second model, we get . This shows that both the models are in quintessence phase. For third model we get accelerated expansion of the Universe. Further, we compare the values of EoS parameter and deceleration parameter with the observational values
A novel approach to baryogenesis in f(Q,Lm) gravity and its cosmological implications
No full textWe present an examination of the f(Q,Lm) gravity model, in which the functional form f(Q,Lm)=αQn+βLm is postulated and discuss its potential impact on cosmological dynamics and the phenomenon of gravitational baryogenesis. Combining observational insights from Hubble, BAO and pantheon datasets, we conduct a comprehensive analysis to constrain the model's parameters and determine the baryon-to-entropy ratio ηBs, providing valuable insights into the model's performance and cosmological implications. In the context of baryogenesis and generalized gravitational baryogenesis, we show that setting n=12 leads to a mathematical inconsistency due to the presence of a division by zero arising from the factor (1−2n) in the denominators. By looking closely at how ηBs changes with n and β, we show that our model predicts a baryon-to-entropy ratio that is both positive and in line with the highest value seen so far, which is 9.42×10−11 for 1.32965<n<1.39252, and this value is right for both β and n, with α≃−1.95084×1086. The excellent agreement between our model's predictions and the pantheon dataset demonstrates the model's capacity to accurately describe the physics of baryogenesis and its ability to reproduce the observed features of the cosmological data, showcasing its potential as a reliable tool for understanding the evolution of the Universe
Barrow Holographic Dark Energy in gravity: A dynamical system perspective
No full textIn this work, we investigate the cosmological implications of the Barrow Holographic Dark Energy (BADE) model within the framework of gravity, specifically considering the model . Using a dynamical system approach for both non-interacting and interacting scenarios, we identify critical points corresponding to different phases of the Universe\u27s evolution, including matter domination, radiation domination and dark energy-driven accelerated expansion. Our analysis reveals two stable critical points in the non-interacting case and three stable critical points in the interacting case, each indicating a transition to a stable phase dominated by BADE. The phase plots clearly demonstrate the evolution of the Universe\u27s dynamics toward these stable points. At these stable points, the deceleration parameter is negative, consistent with accelerated expansion and the equation of state parameter suggests that BADE behaves as a dark energy component. These findings highlight the BADE model\u27s strength as a viable explanation for the Universe\u27s late-time acceleration inside gravity, and they provide novel perspectives on the cosmic development of dark energy-matter interactions.24 pages, 7 figure
Constraining model parameters in f(Q,C) gravity: Observational analysis and geometric diagnostics
No full textWe investigate the cosmological implications of gravity with , where is the non-metricity scalar and encapsulates cosmological expansion terms. Three parameterizations of the EoS for dark energy, , and are tested using the Hubble, Hubble plus BAO, and Hubble plus BAO plus Pantheon datasets to constrain model parameters. The resulting Hubble and deceleration parameters reveal a transition from deceleration to acceleration, supporting current cosmic acceleration observations. Analysis of the energy density and pressure confirms positive energy density and a negative pressure for dark energy, potentially driving the late-time acceleration. We examine energy conditions, showing compliance with NEC, WEC and DEC, while SEC remains negative, supporting an accelerated expansion. Statefinder diagnostics suggest that two of the EoS parameterizations lead to Quintessence-like behavior with a time-varying dark energy component, while the third closely approaches CDM showing slight deviations consistent with recent observations. Sound speed analysis demonstrates the physical stability of all parameterizations.32 pages, 45 figure
A new parametric study of
No full textIn this work, we explore the cosmological dynamics of a modified gravity framework based on the function , where Q denotes the nonmetricity scalar and B is the boundary term that relates Q to the Ricci scalar. The matter sector is modeled using the Modified Chaplygin Gas (MCG) with the equation of state , allowing the model to interpolate between early-time matter behavior and late-time cosmic acceleration. By deriving an analytical expression for the Hubble parameter H(z), we perform a parameter estimation using Markov Chain Monte Carlo (MCMC) techniques in conjunction with the latest cosmological observations: 46 Hubble parameter measurements, 15 BAO data points, DESI DR2 BAO data and the Pantheon+ Type Ia supernovae compilation. The best-fit values are obtained as km/s/Mpc, , and . The deceleration parameter transitions at redshift , while the present-day value is . The model yields an age of the Universe Gyr and a present EoS parameter , which reflects the late-time acceleration consistent with observational bounds. These results demonstrate that the MCG scenario within f(Q, B) gravity provides a viable and observationally consistent framework for explaining the late-time accelerated expansion of the Universe
Stability Analysis of Cosmological models in Gravity
No full textWe investigated the stability condition in gravity theory for
considering two models by using dynamical system. We assume the forms of
are = , =
ln, where , , and be the free
parameters. We evaluated the equilibrium points for these models and examine
the stability behavior. We found five stable critical points for Model I and
three stable critical points for Model II. The phase plots for these systems
are examined and discussed the physical interpretation. We illustrate all the
cosmological parameters such as , , and
at each fixed points and compare the parameters with
observational values. Further, we assume hybrid scale factor and the equation
of redshift and time is
.
We transform all the parameters in redshift by using this equation and examine
the behavior of these parameters. Our models represent the accelerating stage
of the Universe. The energy conditions are examined in terms of redshift and
SEC is not satisfied for the model. We also find the statefinder parameters
in terms of z and discuss the nature of and plane. For
both pairs and our models represent the CDM model.
Hence, we determine that our models are stable and it satisfies all
the observational values
Governmentalizing NRI Philanthropy in Andhra Pradesh: A Transregional Approach to India’s Development
No full textThis chapter looks at the idea of governmentalization of NRI philanthropy in the state of Andhra Pradesh. In a detailed analysis, the author shows how the dominant community of the Kammas in the coastal Andhra region, having historically benefitted from being part of the anti-Brahmin movement, consolidated their identity as the foremost landowners with a concerted effort towards higher education and already established networks enabling them to pursue careers in the USA. This, and a belief in giving back to the village and caste that has enabled their migration and hence success in life, has encouraged philanthropy in the region, in terms of NRI contribution to the NRI cell of Zilla Parishad and the Janmabhoomi project of the then TDP government. This is crucial because, with the term ‘governmentalization ’, she shows how caste interests influence government policy and shape the direction which philanthropy will take, who will be the recipient of the philanthropic measures, how will the philanthropic projects be spatially located and how the existing structures of hegemony will continue in this curious coming together of public and private capital
Partitions: categories and destinies
No full textThe chapter analyzes state partition as a political phenomenon, which has inceasingly occurred in modern times, following new patters as long as a specific form of state has been established in Europe and spread worldwide as a lever for modernity, either through the communist experience or the process of decolonization, via colonization. In this framework the author considers different interpretative categories from dividing without partitions to the applied forms of partitions, the fragility of the terminology and the sources of attractiveness of partitions. Furthermore, the chapter deals with the relations between partitions and democracy, the role of sovereignty and the changes that are transforming the nation states in networking societies. In his conclusions, the author advocates a recasting of statehood as a great challenge, particularly for Europe
Conclusions
No full textIn his book's conclusions, the author elaborates about the nature of partitions as a key challenge for a study devoted to state dismemberment. The international research project that supported an interdisciplinary team of 4 authors to work on this subject at the Columbia Institute of Reid Hall in Paris together with La maison des Sciences de l'homme came in the end to believe that partitions are not the expression of clashes of civilization. Rather, they are a local, but widespread attempt at reacting against globalization by local/global means, patterns, symbols and convictions. They are a lever for multiplying states in a community of states in crisis and unable to govern the world. At the same time, partitions are also a global phenomenon that requires global politics and strategies in order to avoid the risk of multiplying the political cells of human societies, as a fortress of incommunicability in a world of networks and webs. In the end the author stresses how partitions are a litmus paper that human beings need for testing new forms of political organization, representation, and mediation
