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We investigate an impact of the axial-vector interaction on spatial modulation of quark matter. A magnetic field coupled with baryon density leads to a topological axial current, so that the effect of the axial-vector interaction is crucially enhanced then. Using the Sakai-Sugimoto model we have found that, contrary to a naïve expectation, the spatially modulated phase is less favored for a stronger magnetic field, which is realized by the presence of topological current.PACS numbers: 11.25. Tq, 12.38.Mh, Introduction The phase diagram of hot and dense matter out of quarks and gluons has not been clarified satisfactorily based on the first-principle theory of the strong interaction, i.e. quantum chromodynamics (QCD). The most severe obstacle is the notorious sign problem of the Dirac determinant at finite quark density ρ or chemical potential µ, which prevents us from the direct application of the Monte-Carlo simulation in the region with µ T [1].Instead of the lattice simulation, one could have deduced possible phase structures using chiral effective models, see e.g.[2] for a recent work. It is conjectured from model studies that the chiral phase transition might be of first order at high density, so that a second-order critical point called the QCD critical point [3] could appear on the phase diagram, the discovery of which is one of the major goals of the beam-energy scan program in heavy-ion collision experiments [4]. The model setup, however, suffers from uncontrolled uncertainties and the QCD critical point is a model-dependent prediction. It is well understood by now that the vector-type interaction ∼ (ψγ µ ψ) 2 , which gives rise to the density-density interaction ∼ ρ 2 even in the mean-field level, crucially affects the liquid-gas phase transition of dense quark matter [5,6] (see also [7]). Moreover, nowadays, spatially inhomogeneous states are becoming a more and more realistic candidate that may supersede the conventional firstorder phase boundary [8], which is rather robust against the vector interaction [6, 9].The simplest Ansatz to introduce spatial modulation is the chiral spiral or the dual chiral-density wave,

Abstract. The Eulerian perfect-fluid theory is reformulated from its action principle in a pure field-theoretic manner. Conservation of the convective current is no longer imposed by Lin's constraints, but rather adopted as the central idea of the theory. Our formulation, for the first time, successfully reduces redundant degrees of freedom promoting one half of the Clebsch variables as the true dynamical fields. Interactions on these fields allow for the exchange of the convective current of quantities such as mass and charge, which are uniformly understood as the breaking of the underlying symmetry of the force-free fluid. The Clebsch fields play the essential role in the exchange of angular momentum with the force field producing vorticity.

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<p>The use of hydromulches in agriculture is being investigated nowdays by different research groups in their search for harmless materials which mainly exert a reasonable weed control and allow saving crop water consumption by reducing soil evaporation, both in open field as in container nurseries. To achieve these goals, these materials would avoid, or at least reduce, the use of chemical herbicides or plastic mulches derived of non-renewable sources, with the environmental, economy and energy effect it implies, aspects clearly appreciated in organic farming. However, one of the most important problems associated to the hydromulches is their degradation process and their useful life, because, due to their organic origin, may disappear early and therefore not fulfil their function.</p><p>For this reason, in both an intensive almond crop planted in the open field and in young olive trees grown in big containers, we evaluated the evolution and disintegration process of different mixtures based on by-products derived from the agricultural sector (barley straw, rice husk, rests from mushroom production, pruning wood chips), mixed with a binder and recycled paper paste and applied in liquid form on the ground with subsequent solidification (hydromulch). For that, we focused on the evolution of the continuous formation of cracks (shape and size), thickness, puncture resistance and ground cover by the material.</p><p>In summary, and a basis for future tests, the main conclusion derived from the results is the importance of keeping the hydromulch materials as dry as possible. We have been able to verify that, when the material gets wet (either by irrigation water, or by rain or fog), it softens, thus losing its puncture resistance and disappearing early. In addition, when the material becomes wet, the attack of the fauna (rabbits, wild boars, birds, etc.) intensifies, accelerating the process of deterioration of the hydromulch installed on the field. In relation to the materials tested, the hydromulches based on rests from mushroom production undergoes strong and early disintegration, integrating completely into the soil, especially in field conditions. The best results in terms of permanence and stability throughout the trials were obtained in rice husk and pruning wood chips, which would position these mixtures as interesting alternatives especially in container crops, important for nursery crops.</p><p><strong>Keywords</strong>: hydromulches, deterioration, puncture resistance, organic farming.</p><p><strong>Acknowledgements</strong>: Project RTA2015-00047-C05-03 - INIA (Spanish Ministry of Economy and Competitiveness).</p>