On mesoscale strain fluctuations in tensile tests on additively manufactured 17-4PH stainless steel

Additively manufactured materials usually exhibit mesoscale heterogeneities. Mesoscale fluctuations of strain fields in notched samples made of 17-4PH Stainless steel and loaded in tension are investigated. Regularized digital image correlation enables for the analysis of strain fluctuations at different length scales. Five tests on specimen fabricated with different printing parameters are studied. It is shown that the strain fluctuations have no characteristic length scale and are essentially independent of the probed processing parameters.

Dynamical Friction in Nonlocal Gravity

We study dynamical friction in the Newtonian regime of nonlocal gravity (NLG), which is a classical nonlocal generalization of Einstein’s theory of gravitation. The nonlocal aspect of NLG simulates dark matter. The attributes of the resulting effective dark matter are described and the main physical predictions of NLG, which has a characteristic length scale of order 1 kpc, for galactic dynamics are presented. Within the framework of NLG, we derive the analog of Chandrasekhar’s formula for dynamical friction. The astrophysical implications of the results for the apparent rotation of a central bar subject to dynamical friction in a barred spiral galaxy are briefly discussed.

Characteristic Length Scale during the Time Evolution of a Turbulent Bose–Einstein Condensate

Quantum turbulence is characterized by many degrees of freedom interacting non-linearly to produce disordered states, both in space and in time. In this work, we investigate the decaying regime of quantum turbulence in a trapped Bose–Einstein condensate. We present an alternative way of exploring this phenomenon by defining and computing a characteristic length scale, which possesses relevant characteristics to study the establishment of the quantum turbulent regime. We reconstruct the three-dimensional momentum distributions with the inverse Abel transform, as we have done successfully in other works. We present our analysis with both the two- and three-dimensional momentum distributions, discussing their similarities and differences. We argue that the characteristic length allows us to intuitively visualize the time evolution of the turbulent state.

Characteristic Length Scale during the Time Evolution of a Turbulent Bose-Einstein Condensate

Quantum turbulence is characterized by many degrees of freedom interacting non-linearly to produce disordered states, both in space and time. The advances in trapping, cooling, and tuning the interparticle interactions in atomic Bose-Einstein condensates (BECs) make them excellent candidates for studying quantum turbulence. In this work, we investigate the decaying regime of quantum turbulence in a trapped BEC. Although much progress has been made in understanding quantum turbulence, other strategies are needed to overcome some intrinsic difficulties. We present an alternative way of investigating this phenomenon by defining and computing a characteristic length scale, which possesses relevant characteristics to study the establishment of the quantum turbulent regime. One intrinsic difficulty related to these systems is that absorption images of BECs are projected to a plane, thus eliminating some of the information present in the original momentum distribution. We overcome this difficulty by exploring the symmetry of the cloud, which allows us to reconstruct the three-dimensional momentum distributions with the inverse Abel transform. We present our analysis with both the two- and three-dimensional momentum distributions, discussing their similarities and differences. We argue that the characteristic length allows us to visualize the time evolution of the turbulent state intuitively.

Lettau’s Contribution to the Obukhov Length Scale: A Scientific Historical Study

It has been repeatedly assumed that Heinz Lettau found the Obukhov length in 1949 independently of Obukhov in 1946. However, it was not the characteristic length scale, the Obukhov length L, but the ratio of height and the Obukhov length (z/L), the Obukhov stability parameter, that he analyzed. Whether Lettau described the parameter z/L independently of Obukhov is investigated herein. Regardless of speculation about this, the significant contributions made by Lettau in the application of z/L merit this term being called the Obukhov–Lettau stability parameter in the future.

Halo Properties in Helium Nuclei from the Perspective of Geometrical Thermodynamics

The nuclear matter and charge radii of the helium isotopes (A = 4,6,8) are calculated by quantitative geometrical thermodynamics (QGT) taking as input the symmetry of the alpha-particle, the very weak binding (and hence halo nature) of the heavier helium isotopes, and a characteristic length scale given by the proton size. The results follow by considering each isotope in its ground state, with QGT representing each system as a maximum entropy configuration that conforms to the Holographic Principle. This allows key geometric parameters to be determined from the number of degrees of freedom available. QGT treats 6He as a 4He core plus a concentric neutron shell comprising a holomorphic pair of neutrons, and the 8He neutron halo is treated as a holomorphic pair of holomorphic pairs. Considering the information content of each system allows a correlation angle of 2pi/3 between the holomorphic entities to be inferred, and then the charge radii of the three isotopes can be calculated from the displacement of the 4He core from the centre of mass. The calculations for the charge and matter radii of 4,6,8He agree closely with observed values. Similar QGT calculation of the sizes of the self-conjugate A = 4n nuclei {4He,8Be,12C,16O,20Ne,24Mg,28Si,32S,36Ar,40Ca} also agree well with experiment.

Halo Properties in Helium Nuclei From the Perspective of Geometrical Thermodynamics

The nuclear matter and charge radii of the helium isotopes (A=4,6,8) are calculated by quantitative geometrical thermodynamics (QGT) taking as input the symmetry of the a‑particle, the very weak binding (and hence halo nature) of the heavier helium isotopes, and a characteristic length scale given by the proton size. The results follow by considering each isotope in its ground state, with QGT representing each system as a maximum entropy configuration that conforms to the Holographic Principle. This allows key geometric parameters to be determined from the number of degrees of freedom available.QGT treats 6He as a 4He core plus a concentric neutron shell comprising a holomorphic pair of neutrons, and the 8He neutron halo is treated as a holomorphic pair of holomorphic pairs. Considering the information content of each system allows a correlation angle of 2/3 between the holomorphic entities to be inferred, and then the charge radii of the three isotopes can be calculated from the displacement of the 4He core from the centre of mass. The calculations for the charge and matter radii of 4,6,8He agree closely with observed values. Similar QGT calculation of the sizes of the self-conjugate A=4n nuclei {4He,8Be,12C,16O,20Ne,24Mg,28Si,32S,36Ar,40Ca} also agree well with experiment.

Halo Properties in Helium Nuclei From the Perspective of Geometrical Thermodynamics

The nuclear matter and charge radii of the helium isotopes (A=4,6,8) are calculated by quantitative geometrical thermodynamics (QGT) taking as input the symmetry of the a‑particle, the very weak binding (and hence halo nature) of the heavier helium isotopes, and a characteristic length scale given by the proton size. The results follow by considering each isotope in its ground state, with QGT representing each system as a maximum entropy configuration that conforms to the Holographic Principle. This allows key geometric parameters to be determined from the number of degrees of freedom available.QGT treats 6He as a 4He core plus a concentric neutron shell comprising a holomorphic pair of neutrons, and the 8He neutron halo is treated as a holomorphic pair of holomorphic pairs. Considering the information content of each system allows a correlation angle of 2/3 between the holomorphic entities to be inferred, and then the charge radii of the three isotopes can be calculated from the displacement of the 4He core from the centre of mass. The calculations for the charge and matter radii of 4,6,8He agree closely with observed values. Similar QGT calculation of the sizes of the self-conjugate A=4n nuclei {4He,8Be,12C,16O,20Ne,24Mg,28Si,32S,36Ar,40Ca} also agree well with experiment.