The Experts below are selected from a list of 217461 Experts worldwide ranked by ideXlab platform
E. Khan - One of the best experts on this subject based on the ideXlab platform.
-
Incompressibility of finite fermionic systems stable and exotic atomic nuclei
Physical Review C, 2013Co-Authors: E. Khan, Hidetoshi Sagawa, Nils Paar, Dario Vretenar, Gianluca ColòAbstract:The Incompressibility of finite fermionic systems is investigated using analytical approaches and microscopic models. The Incompressibility of a system is directly linked to the zero-point kinetic energy of constituent fermions, and this is a universal feature of fermionic systems. In the case of atomic nuclei, this implies a constant value of the Incompressibility in medium-heavy and heavy nuclei. The evolution of nuclear Incompressibility along Sn and Pb isotopic chains is analyzed using global microscopic models, based on both nonrelativistic and relativistic energy functionals. The result is an almost constant Incompressibility in stable nuclei and systems not far from stability and a steep decrease in nuclei with pronounced neutron excess, caused by the emergence of a soft monopole mode in neutron-rich nuclei.
-
Determination of the density dependence of the nuclear Incompressibility
Physical Review C, 2013Co-Authors: E. Khan, J. MargueronAbstract:The measurements of the isoscalar giant monopole resonance (GMR), also called the breathing mode, are analyzed with respect to their constraints on the quantity $M_c$, e.g. the density dependence of the nuclear Incompressibility around the so-called crossing density $\rho_c$=0.1 fm$^{-3}$. The correlation between the centroid of the GMR, $E_\mathrm{GMR}$, and $M_c$ is shown to be more accurate than the one between $E_\mathrm{GMR}$ and the Incompressibility modulus at saturation density, $K_\infty$, giving rise to an improved determination on the nuclear equation of state. The relationship between $M_c$ and $K_\infty$ is given as a function of the skewness parameter $Q_\infty$ associated to the density dependence of the equation of state. The large variation of $Q_\infty$ among different energy density functionnals directly impacts the knowledge of $K_\infty$: a better knowledge of $Q_\infty$ is required to deduce more accurately $K_\infty$. Using the Local Density Approximation, a simple and accurate expression relating $E_\mathrm{GMR}$ and the quantity $M_c$ is derived and successfully compared to the fully microscopic predictions.
-
Effect of pairing correlations on Incompressibility and symmetry energy in nuclear matter and finite nuclei
Physical Review C, 2010Co-Authors: E. Khan, G Colo, J. Margueron, K. Hagino, H. SagawaAbstract:The role of superfluidity in Incompressibility and in symmetry energy is studied in nuclear matter and finite nuclei. Several pairing interactions are used: surface, mixed, and isovector dependent. Pairing has a small effect on the nuclear matter Incompressibility at saturation density, but the effects are significant at lower densities. The pairing effect on the centroid energy of the isoscalar giant monopole resonance (GMR) is also evaluated for Pb and Sn isotopes by using a microscopic constrained-HFB approach and is found to change at most by 10% the nucleus Incompressibility KA. It is shown by using the local density approximation that most of the pairing effect on the GMR centroid comes from the low-density nuclear surface.
-
The role of superfluidity in nuclear incompressibilities
Physical Review C, 2009Co-Authors: E. KhanAbstract:Nuclei are propitious tools to investigate the role of the superfluidity in the compressibility of a Fermionic system. The centroid of the Giant Monopole Resonance (GMR) in Tin isotopes is predicted using a constrained Hartree-Fock Bogoliubov approach, ensuring a full self-consistent treatment. Superfluidity is found to favour the compressibitily of nuclei. Pairing correlations explain why doubly magic nuclei such as $^{208}$Pb are stiffer compared to open-shell nuclei. Fully self-consistent predictions of the GMR on an isotopic chain should be the way to microscopically extract both the Incompressibility and the density dependence of a given energy functional. The macroscopic extraction of K$_{sym}$, the asymmetry Incompressibility, is questioned. Investigations of the GMR in unstable nuclei are called for. Pairing gap dependence of the nuclear matter Incompressibility should also be investigated.
Patrizio Neff - One of the best experts on this subject based on the ideXlab platform.
-
Polyconvexity of generalized polynomial-type hyperelastic strain energy functions for near-Incompressibility
International Journal of Solids and Structures, 2003Co-Authors: Stefan Hartmann, Patrizio NeffAbstract:Abstract In this article we investigate several models contained in the literature in the case of near-Incompressibility based on invariants in terms of polyconvexity and coerciveness inequality, which are sufficient to guarantee the existence of a solution. These models are due to Rivlin and Saunders, namely the generalized polynomial-type elasticity, and Arruda and Boyce. The extension to near-Incompressibility is usually carried out by an additive decomposition of the strain energy into a volume-changing and a volume-preserving part, where the volume-changing part depends on the determinant of the deformation gradient and the volume-preserving part on the invariants of the unimodular right Cauchy–Green tensor. It will be shown that the Arruda–Boyce model satisfies the polyconvexity condition, whereas the polynomial-type elasticity does not. Therefore, we propose a new class of strain-energy functions depending on invariants. Moreover, we focus our attention on the structure of further isotropic strain-energy functions.
Stefan Hartmann - One of the best experts on this subject based on the ideXlab platform.
-
on plastic Incompressibility within time adaptive finite elements combined with projection techniques
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: Stefan Hartmann, Karsten J Quint, Martin ArnoldAbstract:Abstract This article treats the interpretation of quasi-static finite elements applied to constitutive equations of evolutionary-type as a solution scheme to solve globally differential-algebraic equations. This concept is applied to finite strain viscoplasticity based on a model with non-linear kinematic hardening under the assumption of plastic Incompressibility. The model is based on multiple multiplicative decomposition both for the deformation gradient into an elastic and an inelastic part as well as for the inelastic part into a kinematic hardening (energy storage) and a dissipative part. Both intermediate configurations are described by inelastic right Cauchy–Green tensors satisfying inelastic Incompressibility in the theoretical context. The attention in view of the numerical treatment within finite elements is focused on diagonally implicit Runge–Kutta methods which destroy the assumption of plastic Incompressibility during the time-integration due to an additive structure of the integration step. In combination with a Multilevel-Newton algorithm these algorithms embed the classical strain-driven radial-return method. To this end, a concept of geometric numerical integration is applied, where the plastic Incompressibility condition is taken into account as an additional side-condition. Since the literature states large integration errors if the side-condition is not taken into account, a particular focus lies on the application of a time-adaptive procedure. Accordingly, the article investigates (i) the algorithmic treatment of kinematic hardening within time-adaptive finite elements, (ii) the influence of the Perzyna-type viscoplasticity approach in view of an order reduction phenomenon, and (iii) the influence of taking into account the exact fulfillment of plastic Incompressibility using a projection method having the advantage of simple implementation.
-
Polyconvexity of generalized polynomial-type hyperelastic strain energy functions for near-Incompressibility
International Journal of Solids and Structures, 2003Co-Authors: Stefan Hartmann, Patrizio NeffAbstract:Abstract In this article we investigate several models contained in the literature in the case of near-Incompressibility based on invariants in terms of polyconvexity and coerciveness inequality, which are sufficient to guarantee the existence of a solution. These models are due to Rivlin and Saunders, namely the generalized polynomial-type elasticity, and Arruda and Boyce. The extension to near-Incompressibility is usually carried out by an additive decomposition of the strain energy into a volume-changing and a volume-preserving part, where the volume-changing part depends on the determinant of the deformation gradient and the volume-preserving part on the invariants of the unimodular right Cauchy–Green tensor. It will be shown that the Arruda–Boyce model satisfies the polyconvexity condition, whereas the polynomial-type elasticity does not. Therefore, we propose a new class of strain-energy functions depending on invariants. Moreover, we focus our attention on the structure of further isotropic strain-energy functions.
Wojtanchris - One of the best experts on this subject based on the ideXlab platform.
-
A stream function solver for liquid simulations
ACM Transactions on Graphics, 2015Co-Authors: Andoryoichi, Thuereynils, WojtanchrisAbstract:This paper presents a liquid simulation technique that enforces the Incompressibility condition using a stream function solve instead of a pressure projection. Previous methods have used stream fun...
Stavros Garoufalidis - One of the best experts on this subject based on the ideXlab platform.
-
Incompressibility criteria for spun normal surfaces
Transactions of the American Mathematical Society, 2012Co-Authors: Nathan M Dunfield, Stavros GaroufalidisAbstract:We give a simple sufficient condition for a spun-normal surface in an ideal triangulation to be incompressible, namely that it is a vertex surface with non-empty boundary which has a quadrilateral in each tetrahedron. While this condition is far from being necessary, it is powerful enough to give two new results: the existence of alternating knots with non-integer boundary slopes, and a proof of the Slope Conjecture for a large class of 2-fusion knots.
-
Incompressibility criteria for spun normal surfaces
arXiv: Geometric Topology, 2011Co-Authors: Nathan M Dunfield, Stavros GaroufalidisAbstract:We give a simple sufficient condition for a spun-normal surface in an ideal triangulation to be incompressible, namely that it is a vertex surface with non-empty boundary which has a quadrilateral in each tetrahedron. While this condition is far from being necessary, it is powerful enough to give two new results: the existence of alternating knots with non-integer boundary slopes, and a proof of the Slope Conjecture for a large class of 2-fusion knots. While the condition and conclusion are purely topological, the proof uses the Culler-Shalen theory of essential surfaces arising from ideal points of the character variety, as reinterpreted by Thurston and Yoshida. The criterion itself comes from the work of Kabaya, which we place into the language of normal surface theory. This allows the criterion to be easily applied, and gives the framework for proving that the surface is incompressible. We also explore which spun-normal surfaces arise from ideal points of the deformation variety. In particular, we give an example where no vertex or fundamental surface arises in this way.
