Rescaled density expansions and demixing in hard-sphere binary mixtures

The demixing transition of a binary fluid mixture of additive hard spheres is analyzed for different size asymmetries by starting from the exact low-density expansion of the pressure. Already within the second virial approximation the fluid separates into two phases of different composition with a lower consolute critical point. By successively incorporating the third, fourth, and fifth virial coefficients, the critical consolute point moves to higher values of the pressure and to lower values of the partial number fraction of the large spheres. When the exact low-density expansion of the pressure is rescaled to higher densities as in the Percus-Yevick theory, by adding more exact virial coefficients a different qualitative movement of the critical consolute point in the phase diagram is found. It is argued that the Percus-Yevick factor appearing in many empirical equations of state for the mixture has a deep influence on the location of the critical consolute point, so that the resulting phase diagram for a prescribed equation has to be taken with caution.Comment: 5 pages, 1 figure; to be published in The Journal of Chemical Physic

Cosmology with minimal length uncertainty relations

We study the effects of the existence of a minimal observable length in the phase space of classical and quantum de Sitter (dS) and Anti de Sitter (AdS) cosmology. Since this length has been suggested in quantum gravity and string theory, its effects in the early universe might be expected. Adopting the existence of such a minimum length results in the Generalized Uncertainty Principle (GUP), which is a deformed Heisenberg algebra between minisuperspace variables and their momenta operators. We extend these deformed commutating relations to the corresponding deformed Poisson algebra in the classical limit. Using the resulting Poisson and Heisenberg relations, we then construct the classical and quantum cosmology of dS and Ads models in a canonical framework. We show that in classical dS cosmology this effect yields an inflationary universe in which the rate of expansion is larger than the usual dS universe. Also, for the AdS model it is shown that GUP might change the oscillatory nature of the corresponding cosmology. We also study the effects of GUP in quantized models through approximate analytical solutions of the Wheeler-DeWitt (WD) equation, in the limit of small scale factor for the universe, and compare the results with the ordinary quantum cosmology in each case.Comment: 11 pages, 4 figures, to appear in IJMP

phi-fourth model on a circle

The four dimensional critical scalar theory at equilibrium with a thermal bath at temperature $T$ is considered. The thermal equilibrium state is labeled by $n$ the winding number of the vacua around the compact imaginary-time direction which compactification radius is 1/T. The effective action for zero modes is a three dimensional $\phi^4$ scalar theory in which the mass of the the scalar field is proportional to $n/T$ resembling the Kaluza-Klein dimensional reduction. Similar results are obtained for the theory at zero temperature but in a one-dimensional potential well. Since parity is violated by the vacua with odd vacuum number $n$, in such cases there is also a cubic term in the effective potential. The $\phi^3$-term contribution to the vacuum shift at one-loop is of the same order of the contribution from the $\phi^4$-term in terms of the coupling constant of the four dimensional theory but becomes negligible as $n$ tends to infinity. Finally, the relation between the scalar classical vacua and the corresponding SU(2) instantons on $S^1\times{\mathbb R}^3$ in the 't Hooft ansatz is studied.Comment: 9 pages, revtex4, to appear in Phys.Lett.

Qualitative study in Loop Quantum Cosmology

This work contains a detailed qualitative analysis, in General Relativity and in Loop Quantum Cosmology, of the dynamics in the associated phase space of a scalar field minimally coupled with gravity, whose potential mimics the dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with the orbits (solutions) of the system, we will see that there are analytic ones, which lead to the same dynamics as the perfect fluid, and our goal is to check their stability, depending on the value of the EoS parameter, i.e., to show whether the other orbits converge or diverge to these analytic solutions at early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ

The decivilizing effects of the financial system

This paper focuses on the financial system as a global figuration in order to analyse its social logic of functioning and its connections with certain models of sociability and behaviour. As a global figuration, the financial system can be considered the result of the confluence of a triple vector of forces: a) the formation of competition spirals; b) the constitution of a complex web of interdependences and c) the constitution of a set of limits for the action of external constraints over the participants in the name of financial self-regulation. This triple vector is related to a model of sociability and behaviour based on a) the social production of indifference; b) the logic of the free-rider and c) the promotion of dis-identification patterns between the financial established and the financial outsiders. In sum, this paper proposes a framework of a figurational approach to the financial system, both in its macro- and micro-sociological dimensions.info:eu-repo/semantics/publishedVersio

Possible polarisation and spin dependent aspects of quantum gravity

We argue that quantum gravity theories that carry a Lie algebraic modification of the Poincare' and Heisenberg algebras inevitably provide inhomogeneities that may serve as seeds for cosmological structure formation. Furthermore, in this class of theories one must expect a strong polarisation and spin dependence of various quantum-gravity effects.Comment: Awarded an "honourable mention" in the 2007 Gravity Research Foundation Essay Competitio

Giant Angiolymphoid Hyperplasia with Eosinophilia on the Chest

Angiolymphoid hyperplasia with eosinophilia is a rare vascular proliferation characterized by single or multiple purplish, brownish papules and subcutaneous nodules, sometimes associated with pain or pruritus. This rare benign process occurs with a female predominance. Approximately 85% of the lesions occur in the skin of the head and neck; most of them are around the ear or on the forehead or scalp. Whether angiolymphoid hyperplasia with eosinophilia represents a benign neoplasm or an unusual reaction to varied stimuli, including trauma, the etiology remains unclear. Histopathologically, the lesions consist of a proliferation of blood vessels of variable size lined by large epithelioid endothelial cells and a variable inflammatory infiltrate of lymphocytes and eosinophils, sometimes with lymphoid follicle formation. The lesion is benign but may be persistent and is difficult to eradicate. We report on a case of a 58-year-old Caucasian man who presented a purplish pink dome-shaped tumor of size up to 8 cm in diameter located on the chest. We emphasize this case considering the unusual dimensions of the lesion (8 cm diameter) and the atypical location on the chest