Mass-radius relation for magnetized strange quark stars

We review the stability of magnetized strange quark matter (MSQM) within the phenomenological MIT bag model, taking into account the variation of the relevant input parameters, namely, the strange quark mass, baryon density, magnetic field and bag parameter. A comparison with magnetized asymmetric quark matter in $\beta$-equilibrium as well as with strange quark matter (SQM) is presented. We obtain that the energy per baryon for MSQM decreases as the magnetic field increases, and its minimum value at vanishing pressure is lower than the value found for SQM, which implies that MSQM is more stable than non-magnetized SQM. The mass-radius relation for magnetized strange quark stars is also obtained in this framework.Comment: 7 pages, 6 figures. To be published in the Proceedings of 4th International Workshop on Relativistic Astrophysical and Astronomy IWARA0

Vorticity statistics in the two-dimensional enstrophy cascade

We report the first extensive experimental observation of the two-dimensional enstrophy cascade, along with the determination of the high order vorticity statistics. The energy spectra we obtain are remarkably close to the Kraichnan Batchelor expectation. The distributions of the vorticity increments, in the inertial range, deviate only little from gaussianity and the corresponding structure functions exponents are indistinguishable from zero. It is thus shown that there is no sizeable small scale intermittency in the enstrophy cascade, in agreement with recent theoretical analyses.Comment: 5 pages, 7 Figure

Pemodelan Inundasi (Banjir Rob) Di Pesisir Kota Semarang Dengan Menggunakan Model Hidrodinamika

Fenomena banjir rob yang terjadi di Semarang sudah sangat memprihatinkan, karena banjir ini tidak hanya terjadi pada daerah pesisir pantai saja tetapi sudah menggenangi wilayah pariwisata, pemukiman, maupun industri. Tujuan penelitian ini adalah untuk menghitung jarak dan luas genangan rob di pesisir Kota Semarang akibat kondisi pasang surut pada saat purnama dan perbani.Metode yang digunakan dalam penelitian ini adalah metode kuantitatif. Penelitian dibagi menjadi tiga tahap, yaitu pengumpulan data sekunder, pengambilan data lapangan, dan pengolahan data. Pengambilan data lapangan dilakukan di perairan Kota Semarang yang dilaksanakan dari tanggal 5 - 20 Juli 2010 pada koordinat 6052'30”- 6057'30” LS dan 110019'45”-110027'30” BT. Pengolahan data serta proses pemodelan dilakukan di BPPT, Yogyakarta. Berdasarkan hasil penelitian diketahui bahwa arus di daerah penelitian didominasi oleh arus pasang surut sebesar 74,3%, dimana pergerakannya condong dari arah utara ke selatan dengan kecepatan rata-rata terhadap kedalaman mencapai 0,024 m/s. Sedangkan dari hasil analisis banjir rob (inundasi), jarak terjauh terjadi di kecamatan Genuk yang mencapai 4,295 km dari garis pantai pada saat pasang purnama dan jarak terdekat terjadi di kecamatan Semarang Barat yang mencapai 488,93 m dari garis pantai pada saat pasang perbani. Selain itu berdasarkan hasil penelitian didapat luas banjir maksimal terjadi di kecamatan Tugu dengan luas 3450,1 Ha pada saat pasang purnama. Sedangkan wilayah yang paling sedikit terendam terjadi di kecamatan Gayamsari dengan luas 71,228 Ha pada saat pasang perbani. Hasil verifikasi bathimetri mempunyai tingkat kebenaran sekitar 73,69%, pasut sekitar 84,87%, vektor u dan v arus lapangan sekitar 93,58% dan model sekitar 92%

Experimental study of Taylor's hypothesis in a turbulent soap film

An experimental study of Taylor's hypothesis in a quasi-two-dimensional turbulent soap film is presented. A two probe laser Doppler velocimeter enables a non-intrusive simultaneous measurement of the velocity at spatially separated points. The breakdown of Taylor's hypothesis is quantified using the cross correlation between two points displaced in both space and time; correlation is better than 90% for scales less than the integral scale. A quantitative study of the decorrelation beyond the integral scale is presented, including an analysis of the failure of Taylor's hypothesis using techniques from predictability studies of turbulent flows. Our results are compared with similar studies of 3D turbulence.Comment: 27 pages, + 19 figure

Closure of two dimensional turbulence: the role of pressure gradients

Inverse energy cascade regime of two dimensional turbulence is investigated by means of high resolution numerical simulations. Numerical computations of conditional averages of transverse pressure gradient increments are found to be compatible with a recently proposed self-consistent Gaussian model. An analogous low order closure model for the longitudinal pressure gradient is proposed and its validity is numerically examined. In this case numerical evidence for the presence of higher order terms in the closure is found. The fundamental role of conditional statistics between longitudinal and transverse components is highlighted.Comment: 4 pages, 2 figures, in press on PR

Magnetized strangelets at finite temperature

The main properties of magnetized strangelets, namely, their energy per baryon, radius and electric charge, are studied. Temperature effects are also taken into account in order to study their stability compared to the 56Fe isotope and non-magnetized strangelets using the liquid drop model. Massive quarks are considered with the aim to have a more realistic description for strangelets in the astrophysical context and the environment of heavy ion colliders, playing also an important role in the thermodynamical quantities of the quark gas. It is concluded that the presence of a magnetic field tends to stabilize more the strangelets, even when temperature effects are taken into account. Magnetized strangelets in a paired superconductor phase (magnetized color flavor locked phase) are also discussed. It is shown that they are more stable than ordinary magnetized strangelets for typical gap values of the order of O(100) MeV.Comment: 10 pages, 10 figures, discussion extended, new references adde

Universality and saturation of intermittency in passive scalar turbulence

The statistical properties of a scalar field advected by the non-intermittent Navier-Stokes flow arising from a two-dimensional inverse energy cascade are investigated. The universality properties of the scalar field are directly probed by comparing the results obtained with two different types of injection mechanisms. Scaling properties are shown to be universal, even though anisotropies injected at large scales persist down to the smallest scales and local isotropy is not fully restored. Scalar statistics is strongly intermittent and scaling exponents saturate to a constant for sufficiently high orders. This is observed also for the advection by a velocity field rapidly changing in time, pointing to the genericity of the phenomenon. The persistence of anisotropies and the saturation are both statistical signatures of the ramp-and-cliff structures observed in the scalar field.Comment: 4 pages, 8 figure

Intermittency in Dynamics of Two-Dimensional Vortex-like Defects

We examine high-order dynamical correlations of defects (vortices, disclinations etc) in thin films starting from the Langevin equation for the defect motion. We demonstrate that dynamical correlation functions $F_{2n}$ of vorticity and disclinicity behave as $F_{2n}\sim y^2/r^{4n}$ where $r$ is the characteristic scale and $y$ is the fugacity. As a consequence, below the Berezinskii-Kosterlitz-Thouless transition temperature $F_{2n}$ are characterized by anomalous scaling exponents. The behavior strongly differs from the normal law $F_{2n}\sim F_2^n$ occurring for simultaneous correlation functions, the non-simultaneous correlation functions appear to be much larger. The phenomenon resembles intermittency in turbulence.Comment: 30 pages, 11 figure

Recent Developments in Understanding Two-dimensional Turbulence and the Nastrom-Gage Spectrum

Two-dimensional turbulence appears to be a more formidable problem than three-dimensional turbulence despite the numerical advantage of working with one less dimension. In the present paper we review recent numerical investigations of the phenomenology of two-dimensional turbulence as well as recent theoretical breakthroughs by various leading researchers. We also review efforts to reconcile the observed energy spectrum of the atmosphere (the spectrum) with the predictions of two-dimensional turbulence and quasi-geostrophic turbulence.Comment: Invited review; accepted by J. Low Temp. Phys.; Proceedings for Warwick Turbulence Symposium Workshop on Universal features in turbulence: from quantum to cosmological scales, 200

A striking correspondence between the dynamics generated by the vector fields and by the scalar parabolic equations

The purpose of this paper is to enhance a correspondence between the dynamics of the differential equations $\dot y(t)=g(y(t))$ on $\mathbb{R}^d$ and those of the parabolic equations $\dot u=\Delta u +f(x,u,\nabla u)$ on a bounded domain $\Omega$. We give details on the similarities of these dynamics in the cases $d=1$, $d=2$ and $d\geq 3$ and in the corresponding cases $\Omega=(0,1)$, $\Omega=\mathbb{T}^1$ and dim($\Omega$)$\geq 2$ respectively. In addition to the beauty of such a correspondence, this could serve as a guideline for future research on the dynamics of parabolic equations