arXiv subjects

Hirofumi Ohta

Publications and source records attributed to Hirofumi Ohta.

3 recordsLinked to original sources

arXiv2017

On Estimation of Conditional Modes Using Multiple Quantile Regressions

We propose an estimation method for the conditional mode when the conditioning variable is high-dimensional. In the proposed method, we first estimate the conditional density by solving quantile regressions multiple times. We then estimate the conditional mode by finding the maximum of the estimated conditional density. The proposed method has two advantages in that it is computationally stable because it has no initial parameter dependencies, and it is statistically efficient with a fast convergence rate. Synthetic and real-world data experiments demonstrate the better performance of the proposed method compared to other existing ones.

stat.ML↗

arXiv2006

Parity-projected Skyrme Hartree-Fock and angular momentum projection approach to Mg isotopes

We perform calculations of the variation after parity projection with Skyrme interaction for ground and excited states of even-even Mg isotopes. Using the 3D real-space representation, we can take into account any kind of deformation; e.g., cluster structure, gamma-deformation. We also perform the full 3D angular momentum projection to obtained rotational spectra and B(E2). In 24Mg, the ground K^pi=0+ and several odd-parity bands are calculated. In 30,32,34Mg, our calculation reproduces a breaking of the N=20 magic number, so-called "Island of inversion" phenomena. Properties of both the ground and excited states are reasonably reproduced.

nucl-th↗

arXiv2004

Variation after parity projection calculation with Skyrme interaction for light nuclei

A self-consistent calculation with variation after parity projection is proposed to study both ground and excited states of light nuclei. This procedure provides description of the ground state incorporating some correlation effects, and self-consistent solutions for the excited states of negative parity. For flexible description of nuclear shapes, single particle orbitals are represented on a uniform grid in the three-dimensional Cartesian coordinates. The angular momentum projection is performed after variation to calculate rotational spectra. To demonstrate the usefulness of the method, results are shown for two N=Z nuclei, 20Ne and 12C, for which clustering correlations are known to be important. In the 20Ne nucleus, both cluster-like and shell-model-like states are described simultaneously in the present framework. For 12C nucleus, the appearance of three-alpha clustering correlation in the ground state is investigated in relation to the strength of the two-body spin-orbit interaction.

nucl-th↗