A mixing interpolation method to mimic pasta phases in compact star matter

We present a new method to interpolate between two matter phases that allows for a description of mixed phases and can be used, e.g., for mimicking transitions between pasta structures occuring in the crust as well as in the inner core of compact stars. This interpolation method is based on assuming switch functions that are used to define a mixture of subphases while fulfilling constraints of thermodynamic stability. The width of the transition depends on a free parameter, the pressure increment relative to the critical pressure of a Maxwell construction. As an example we present a trigonometric function ansatz for the switch function together with a pressure increment during the transition. We note that the resulting mixed phase equation of state bears similarities with the appearance of substitutional compounds in neutron star crusts and with the sequence of transitions between different pasta phases in the hadron-to-quark matter transition. We apply this method to the case of a hadron-to-quark matter transition and test the robustness of the compact star mass twin phenomenon against the appearance of pasta phases modeled in this way.Comment: 8 pages, 9 figures, 2 tables, revised version accepted for publication in Eur. Phys. J.

Mass-radius constraints for compact stars and a critical endpoint

We present two types of models for hybrid compact stars composed of a quark core and a hadronic mantle with an abrupt first order phase transition at the interface which are in accordance with the latest astrophysical measurements of two 2 M_sun pulsars. While the first is a schematic one, the second one is based on a QCD motivated nonlocal PNJL model with density-dependent vector coupling strength. Both models support the possibility of so called twin compact stars which have the same mass but different radius and internal structure at high mass (~2 M_sun), provided they exhibit a large jump \Delta \epsilon in the energy density of the first order phase transition fulfilling \Delta \epsilon/\epsilon_crit > 0.6. We conclude that the measurement of high-mass twin stars would support the existence of a first order phase transition in symmetric matter at zero temperature entailing the existence of a critical end point in the QCD phase diagram.Comment: 7 pages, 2 figures, 1 table, prepared for the Proceedings of the 8th International Workshop on "Critical Point and Onset of Deconfinement",March 11 to 15, 2013, Napa, California, US

Measuring intangibles' productivity. Empirical evidence from Spanish firms

As companies and shareholders begin to note the potential repercussions of intangible assets upon business results, the inability of the traditional financial statement model to reflect these new ways of creating business value has become evident. Companies have widely adopted new management tools, covering in this way the inability of the traditional financial statement model to reflect these new ways of creating business value. However, there are few prior studies measuring on a quantifiable manner the level of productivity unexplained in the financial statements. In this study, we measure the effect of intangible assets on productivity using data from Spanish firms selected randomly by size and sector over a ten-year period, from 1995 to 2004. Through a sample of more than 10,000 Spanish firms we analyse to what extent labour productivity can be explained by physical capital deepening, by quantified intangible capital deepening and by firm’s economic efficiency (or total factor productivity –PTF). Our results confirm the hypothesis that PTF weigh has increased during the period studied, especially on those firms that have experienced a significant raise in quantified intangible capital, evidencing that there are some important complementary effects between capital investment and intangible resources in the explanation of productivity growth. These results have significant differences considering economic sector and firm’s dimension.Intangibles, Accounting, Spain

Implications from GW170817 and I-Love-Q relations for relativistic hybrid stars

Gravitational wave observations of GW170817 placed bounds on the tidal deformabilities of compact stars allowing one to probe equations of state for matter at supranuclear densities. Here we design new parametrizations for hybrid hadron-quark equations of state, that give rise to low-mass twin stars, and test them against GW170817. We find that GW170817 is consistent with the coalescence of a binary hybrid star--neutron star. We also test and find that the I-Love-Q relations for hybrid stars in the third family agree with those for purely hadronic and quark stars within $\sim 3\%$ for both slowly and rapidly rotating configurations, implying that these relations can be used to perform equation-of-state independent tests of general relativity and to break degeneracies in gravitational waveforms for hybrid stars in the third family as well.Comment: 8 pages, 4 figures, 2 tables; matches published version, updated fig.