Dynamics of Interacting Quintessence Models: Observational Constraints

Interacting quintessence models have been proposed to explain or, at least, alleviate the coincidence problem of late cosmic acceleration. In this paper we are concerned with two aspects of these kind of models: (i) the dynamical evolution of the model of Chimento et al. [L.P. Chimento, A.S. Jakubi, D. Pavon, and W. Zimdahl, Phys. Rev. D 67, 083513 (2003).], i.e., whether its cosmological evolution gives rise to a right sequence of radiation, dark matter and dark energy dominated eras, and (ii) whether the dark matter dark energy ratio asymptotically evolves towards a non-zero constant. After showing that the model correctly reproduces these eras, we correlate three data sets that constrain the interaction at three redshift epochs: $z\le 10^{4}$, $z=10^{3}$, and $z=1$. We discuss the model selection and argue that even if the model under consideration fulfills both requirements, it is heavily constrained by observation. The prospects that the coincidence problem can be explained by the coupling of dark matter to dark energy are not clearly favored by the data.Comment: 16 pages, 7 figures and 3 tables. Modifications introduced to match published versio

Party Mobile iOS Application

The Party Mobile Application project was created in order to give users the power of a surround sound system at their fingertips. Following the ideas of apps such as AmpMe and SoundSeeder this application aims to synchronize audio between phones in order to play music. Just like surround speakers, these phones would play music throughout a room, car, or house for the enjoyment of users. Party Mobile also aims to give people the ability to share their music with the rest of the world with its playlist upload functionality. Any user can upload a playlist of their music to the application’s server, and then play it in a session for a group of people. Additionally, all playlists uploaded to the server are public so users can also listen to playlists compiled by other people. With its various functionalities, the Party Mobile Application aims to give users the ability to share, listen, and enjoy music with their friends anywhere in the world. The application accomplishes this goal through two primary means. The first is utilizing Bluetooth as the primary method of communication between devices. All phones in a session connect to each other using Bluetooth and send each other the necessary data to play music synchronized. Alternatively, the application can also use wifi to send data to phones; however, this method is situational based on the security settings of whatever network your phone is on. In addition, to this, the application also uses an Amazon AWS server to store all of the playlists created by users. Utilizing the Swift coding language Party Mobile is able to interact with the AWS server directly, and download songs and playlists to user phones. These two parts of the application, when put together, create the experience that Party Mobile was created to give its users. In the rest of this report, readers can learn about the details behind the apps two main features as well as the development cycle of the application

Matter density perturbations in interacting quintessence models

Models with dark energy decaying into dark matter have been proposed to solve the coincidence problem in cosmology. We study the effect of such coupling in the matter power spectrum. Due to the interaction, the growth of matter density perturbations during the radiation dominated regime is slower compared to non-interacting models with the same ratio of dark matter to dark energy today. This effect introduces a damping on the power spectrum at small scales proportional to the strength of the interaction and similar to the effect generated by ultrarelativistic neutrinos. The interaction also shifts matter--radiation equality to larger scales. We compare the matter power spectrum of interacting quintessence models with the measurments of 2dFGRS. We particularize our study to models that during radiation domination have a constant dark matter to dark energy ratio.Comment: 11 pages, 4 figures, accepted for publication in Phys. Rev.