Magnetized strange quark matter and magnetized strange quark stars

Strange quark matter could be found in the core of neutron stars or forming strange quark stars. As is well known, these astrophysical objects are endowed with strong magnetic fields which affect the microscopic properties of matter and modify the macroscopic properties of the system. In this paper we study the role of a strong magnetic field in the thermodynamical properties of a magnetized degenerate strange quark gas, taking into account beta-equilibrium and charge neutrality. Quarks and electrons interact with the magnetic field via their electric charges and anomalous magnetic moments. In contrast to the magnetic field value of 10^19 G, obtained when anomalous magnetic moments are not taken into account, we find the upper bound B < 8.6 x 10^17 G, for the stability of the system. A phase transition could be hidden for fields greater than this value.Comment: 9 pages, 9 figure

Yield Management under the Real Options Scheme for Optimal Decision Making in Hotels

Yield management is the process of actively managing inventory to maximize revenues. In this paper we present a model demised to apply yield management techniques using real options to the problem of optimal decision making when assigning rooms to hotel customers. Two different methods are proposed to carry out the evaluation: numerical resolution with the PDEs and Monte Carlo simulation. The achieved results using both methods are similar demonstrating the robustness of the simulation in this field and the model lends itself to be a tool for helping the hotel manager in his operational decision of whether or not giving a room to a potential client

Natural Gauge and Gravitational Coupling Unification and the Superpartner Masses

The possibility to achieve unification at the string scale in the context of the simplest supersymmetric grand unified theory is investigated. We find conservative upper bounds on the superpartner masses consistent with the unification of gauge and gravitational couplings, M_{\tilde G} < 5 TeV and M_{\tilde f} < 3 \times 10^7 GeV, for the superparticles with spin one-half and zero, respectively. These bounds hint towards the possibility that this supersymmetric scenario could be tested at future colliders, and in particular, at the forthcoming LHC.Comment: 8 pages, 4 figures, version accepted in Physics Letters

Constraints on the braneworld from compact stars

According to the braneworld idea, ordinary matter is confined on a 3-dimensional space (brane) that is embedded in a higher-dimensional space-time where gravity propagates. In this work, after reviewing the limits coming from general relativity, finiteness of pressure and causality on the brane, we derive observational constraints on the braneworld parameters from the existence of stable compact stars. The analysis is carried out by solving numerically the brane-modified Tolman-Oppenheimer-Volkoff equations, using different representative equations of state to describe matter in the star interior. The cases of normal dense matter, pure quark matter and hybrid matter are considered.Comment: 13 pages, 11 figures, 2 tables; new EoS considered, references and comments adde

On Connections Between Invariants of Singularities in Zero and Positive Characteristics.

In the first part we study the partition given by the regions where the mixed test ideals are constant. We show that each region can be described as a p-fractal. In addition, we give some examples illustrating that these regions do not need to be composed of finitely many rational polytopes. In the second part we introduce two families of ideals, F-jumping ideals and F-Jacobian ideals, in order to study the singularities of hypersurfaces in positive characteristic. In addition, we use F-Jacobian ideals to study intrinsic properties of the singularities of hypersurfaces. In particular, we give conditions for F-regularity. Moreover, we prove several properties of F-Jacobian ideals that resemble those of Jacobian ideals of polynomials.PhDMathematicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113512/1/juanfp_1.pd

Modelling the evaporation of cryogenic liquids in storage tanks

Cryogenic liquids are substances with a normal boiling point below -150°C. Recently, the interest in cryogenic liquids has skyrocketed because of their role in the energy transition, particularly for LNG and liquid hydrogen. Cryogenic liquids are stored in highly insulated tanks, which are nevertheless subject to heat ingress from the surroundings. The heat ingress drives thermal stratification, natural convection, pressure build-up and evaporation. Managing the evaporated cryogen, denominated boil-off gas (BOG), pose techno-economic, safety and environmental challenges. To facilitate the design and operation of cryogenic storage tanks, new models for cryogenic liquids evaporation have been developed. For isobaric storage, a 1-D model has been developed. The model includes wall heating, heat conduction and advection in the vapour phase. The model shows that advection dominates vapour heat transfer. A 2-D CFD model has been developed to validate the assumptions of the 1-D model. The CFD model validates the 1-D model assumption of one-dimensional advective flow. Additionally, the CFD model shows that thermal stratification dampens natural convection in the vapour. Analytical solutions of the 1-D model valid for the pseudo-steady state have been developed. The analytical solutions constitute an easy-to-use tool for practitioners to improve BOG management. For non-isobaric storage, a 1-D model that considers wall heating, heat conduction and wall boiling has been developed. The 1-D model demonstrates that wall boiling is relevant even for low heat fluxes. The 1-D model predictions were in good agreement with experimental pressure and vapour temperature profiles. The assumptions of the 1-D model have been validated by developing a new single-phase CFD model. A multiphase model has been developed to investigate interfacial transport phenomena. It shows that interfacial momentum transfer slightly enhances liquid heat transfer, and that vapour heating dominates pressure build-up at the beginning of the storage period.Open Acces