Impact of string and monopole-type junctions on domain wall dynamics: implications for dark energy

We investigate the potential role of string and monopole-type junctions in the frustration of domain wall networks using a velocity-dependent one-scale model for the characteristic velocity, $v$, and the characteristic length, $L$, of the network. We show that, except for very special network configurations, v^2 \lsim (HL)^2 \lsim (\rho_\sigma + \rho_\mu)/\rho_m where $H$ is the Hubble parameter and $\rho_\sigma$, $\rho_\mu$ and $\rho_m$ are the average density of domain walls, strings and monopole-type junctions. We further show that if domain walls are to provide a significant contribution to the dark energy without generating exceedingly large CMB temperature fluctuations then, at the present time, the network must have a characteristic length L_0 \lsim 10 \Omega_{\sigma 0}^{-2/3} {\rm kpc} and a characteristic velocity v_0 \lsim 10^{-5} \Omega_{\sigma 0}^{-2/3} where $\Omega_{\sigma 0}=\rho_{\sigma 0}/\rho_{c 0}$ and $\rho_c$ is the critical density. In order to satisfy these constraints with $\Omega_{\sigma 0} \sim 1$, $\rho_{m 0}$ would have to be at least 10 orders of magnitude larger than $\rho_{\sigma 0}$, which would be in complete disagreement with observations. This result provides very strong additional support for the conjecture that no natural frustration mechanism, which could lead to a significant contribution of domain walls to the dark energy budget, exists.Comment: 4 pages, 1 figur

Quintessence and tachyon dark energy models with a constant equation of state parameter

In this work we determine the correspondence between quintessence and tachyon dark energy models with a constant dark energy equation of state parameter, $w_e$. Although the evolution of both the Hubble parameter and the scalar field potential with redshift is the same, we show that the evolution of quintessence/tachyon scalar fields with redshift is, in general, very different. We explicity demonstrate that if $w_e \neq -1$ the potentials need to be very fine-tuned for the relative perturbation on the equation of state parameter, $\Delta w_e/(1+w_e) \ll 1$, to be very small around the present time. We also discuss possible implications of our results for the reconstruction of the evolution of $w_e$ with redshift using varying couplings.Comment: 9 pages, 2 figures, published version with two extra references include

The growth of linear perturbations in generic defect models for structure formation

We study the growth of linear perturbations induced by a generic causal scaling source as a function of the cosmological parameters $h$, $\Omega^m_0$ and $\Omega^\Lambda_0$. We show that for wavenumbers k \gsim 0.01 h/Mpc the spectrum of density and velocity perturbations scale in a similar way to that found in inflationary models with primordial perturbations. We show that this result is independent of the more or less incoherent nature of the source, the small scale power spectrum of the source and of deviations from scaling which naturally occur at late times if $\Omega^m_0 \neq 1$.Comment: 4 pages, 2 figure

The role of domain wall junctions in Carter's pentahedral model

The role of domain wall junctions in Carter's pentahedral model is investigated both analytically and numerically. We perform, for the first time, field theory simulations of such model with various initial conditions. We confirm that there are very specific realizations of Carter's model corresponding to square lattice configurations with X-type junctions which could be stable. However, we show that more realistic realizations, consistent with causality constraints, do lead to a scaling domain wall network with Y-type junctions. We determine the network properties and discuss the corresponding cosmological implications, in particular for dark energy.Comment: 6 pages, 6 figure

Scaling of cosmological domain wall networks with junctions

We describe the results of the largest and most accurate three-dimensional field theory simulations of domain wall networks with junctions. We consider a previously introduced class of models which, in the limit of large number $N$ of coupled scalar fields, approaches the so-called `ideal' model (in terms of its potential to lead to network frustration). We consider values of $N$ between N=2 and N=20. In all cases we find compelling evidence for a gradual approach to scaling, with the quantitative scaling parameters having only a mild dependence on $N$. These results strongly support our no-frustration conjecture.Comment: 4 pages, 2 figure

Confession and political normativity: control of subjectivity and production of the subject

The theme of confession, present in the reflection of Michel Foucault since the early 1960s, pursued the same direction of his researches from the late 1970s concerning the problem of government and the studies of governmentality. Under this perspective, confession is taken as recognition through which the subject authenticates in himself or herself his or her own actions and thoughts. Therefore, it is not only a verbal act by means of which the subject states the truth of his or her being; confession also binds the subject to truth, throwing him or her in a relation of dependency regards the other, and, at the same time, modifying the relationship that he or she establishes with himself or herself. According to Foucault, this is what explains the massive growth of practices of confession in Western societies up until their actual inscription at the heart of procedures of individualization typical of modern political power. This paper explores Foucault’s analysis of confessional practices and its recent developments in the work of Giorgio Agamben (Opus Dei. Archeologia dell’Ufficio, 2012) and Roberto Esposito (Due. La macchina della teologia politica e il posto del pensiero, 2013).El tema de la confesión, presente en la reflexión de Michel Foucault desde principios del decenio de 1960, persiguió la misma dirección de sus investigaciones a partir de finales de 1970 en relación con el problema del gobierno y de los estudios de la gubernamentalidad. Bajo esta perspectiva, la confesión se toma como reconocimiento a través de la cual el sujeto autentica en sí mismo sus propias acciones y pensamientos. Por lo tanto, no es solo un acto verbal por medio del cual el sujeto establece la verdad de su ser; la confesión también une el sujeto a la verdad, colocándolo en una relación de dependencia con el otro y, al mismo tiempo, cambiando la relación que él establece consigo mismo. Según Foucault, esto es lo que explica el crecimiento masivo de las prácticas de la confesión en las sociedades occidentales hasta su inscripción efectiva en el corazón de los procedimientos de individualización del poder político moderno. Este artículo explora el análisis de Foucault de las prácticas confesionales y sus recientes avances en el trabajo de Giorgio Agamben (Opus Dei. Archeologia dell’Ufficio, 2012) y Roberto Esposito (Due. La macchina della teologia politica e il posto del pensiero, 2013)

Lepton flavor violation beyond the MSSM

Most extensions of the Standard Model lepton sector predict large lepton flavor violating rates. Given the promising experimental perspectives for lepton flavor violation in the next few years, this generic expectation might offer a powerful indirect probe to look for new physics. In this review we will cover several aspects of lepton flavor violation in supersymmetric models beyond the Minimal Supersymmetric Standard Model. In particular, we will concentrate on three different scenarios: high-scale and low-scale seesaw models as well as models with R-parity violation. We will see that in some cases the LFV phenomenology can have characteristic features for specific scenarios, implying that dedicated studies must be performed in order to correctly understand the phenomenology in non-minimal supersymmetric models.Comment: 47 pages, 11 figures; v3: references added. Prepared for "Supersymmetry beyond the NMSSM

Theory and phenomenology of lepton flavor violation

The field of lepton flavor violation will live an era of unprecedented developments in the near future, with dedicated experiments in different fronts. The observation of a flavor violating process involving charged leptons would be a clear evidence of physics beyond the Standard Model, thus motivating the great effort in this direction. Furthermore, in case a positive signal is found, a proper theoretical understanding of the lepton flavor anatomy of a given model would become necessary. Here I briefly review the current situation, emphasizing the most relevant theoretical and phenomenological aspects of several processes. Finally, I discuss two topics that have received some attention recently: lepton flavor violation in low-scale seesaw models and lepton flavor violating Higgs decays.Comment: Proceedings of the 8th International Workshop on the CKM Unitarity Triangle (CKM 2014), Vienna, Austria, September 8-12, 201

Interacting viscous matter with a dark energy fluid

We study a cosmological model composed of a dark energy fluid interacting with a viscous matter fluid in a spatially flat Universe. The matter component represents the baryon and dark matter and it is taken into account, through a bulk viscosity, the irreversible process that the matter fluid undergoes because of the accelerated expansion of the universe. The bulk viscous coefficient is assumed to be proportional to the Hubble parameter. The radiation component is also taken into account in the model. The model is constrained using the type Ia supernova observations, the shift parameter of the CMB, the acoustic peak of the BAO and the Hubble expansion rate, to constrain the values of the barotropic index of dark energy and the bulk viscous coefficient. It is found that the bulk viscosity is constrained to be negligible (around zero) from the observations and that the barotropic index for the dark energy to be negative and close to zero too, indicating a phantom energy.Comment: 10 pages, 2 figure