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Context. Dense molecular filaments are ubiquituous in the interstellar medium, yet their internal physical conditions and formation mechanism remain debated. Aims. We study the kinematics and physical conditions in the Musca filament and the Chamaeleon-Musca complex to constrain the physics of filament formation. Methods. We produced CO(2-1) isotopologue maps with the APEX telescope that cut through the Musca filament. We further study a NANTEN2 $^{12}$CO(1-0) map of the Musca cloud and the HI emission of the Chamaeleon-Musca complex. Results. The Musca cloud contains multiple velocity components. Radiative transfer modelling of the CO emission indicates that the Musca filament consists of a cold ($\sim$10 K), dense (n$_{H_2}\sim$10$^4$ cm$^{-3}$) crest, which is best described with a cylindrical geometry. Connected to the crest, a separate gas component at T$\sim$15 K and n$_{H_2}\sim$10$^3$ cm$^{-3}$ is found, the so-called strands. The filament crest has a transverse velocity gradient that is linked to the kinematics of the nearby ambient cloud. Studying the large scale kinematics, we find coherence of the asymmetric kinematics from the 50 pc HI cloud down to the Musca filament. We also report a strong [C$^{18}$O]/[$^{13}$CO] abundance drop by an order of magnitude from the filament crest to the strands over a distance $<$ 0.2 pc in a weak far-ultraviolet (FUV) field. Conclusions. The dense Musca filament crest is a long-lived (several crossing times), dynamic structure that can form stars in the near future because of continuous mass accretion. This mass accretion appears to be triggered by a HI cloud-cloud collision, which bends the magnetic field around dense filaments. This bending of the magnetic field is then responsible for the observed asymmetric accretion scenario of the Musca filament, which is, for instance, seen as a V-shape in the position-velocity (PV) diagram., Comment: 24 pages, 26 figures

We find systematic signatures suggesting a different superconducting nature for a triple-layered cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ with respect to a double-layer through the properties of intrinsic Josephson junctions (IJJs). Our measurements on the current-voltage characteristics reveal that the $c$-axis maximum Josephson current density is sensitive to the superfluid density in outer planes while the critical temperature and the superconducting gap remain unaffected. Switching dynamics of stacked IJJs exhibit that the fluctuation in gauge-invariant phase difference of an IJJ implies that the inner plane completely shields the capacitive coupling between adjacent IJJs, which is essential for mono- and bilayered cuprates., Comment: 10 pages, 2 figures

The ground-state energies and radii for $^{4}$He, $^{16}$O, and $^{40}$Ca are calculated with the unitary-model-operator approach (UMOA). In the present study, we employ the similarity renormalization group (SRG) evolved nucleon-nucleon ($NN$) and three-nucleon ($3N$) interactions based on the chiral effective field theory. This is the first UMOA calculation with both $NN$ and $3N$ interactions. The calculated ground-state energies and radii are consistent with the recent {\it ab initio} results with the same interaction. We evaluate the expectation values with two- and three-body SRG evolved radius operators, in addition to those with the bare radius operator. With the aid of the higher-body evolution of radius operator, it is seen that the calculated radii tend to be SRG resolution-scale independent. We find that the SRG evolution gives minor modifications for the radius operator., Comment: 11 pages, 7 figures

We present a new analysis of the interstellar protons toward the TeV $\gamma$-ray SNR RX J0852.0$-$4622 (G266.2$-$1.2, Vela Jr.). We used the NANTEN2 $^{12}$CO($J$ = 1-0) and ATCA & Parkes HI datasets in order to derive the molecular and atomic gas associated with the TeV $\gamma$-ray shell of the SNR. We find that atomic gas over a velocity range from $V_\mathrm{LSR}$ = $-4$ km s$^{-1}$ to 50 km s$^{-1}$ or 60 km s$^{-1}$ is associated with the entire SNR, while molecular gas is associated with a limited portion of the SNR. The large velocity dispersion of the HI is ascribed to the expanding motion of a few HI shells overlapping toward the SNR but is not due to the Galactic rotation. The total masses of the associated HI and molecular gases are estimated to be $\sim2.5 \times 10^4 $ $M_{\odot}$ and $\sim10^3$ $M_{\odot}$, respectively. A comparison with the H.E.S.S. TeV $\gamma$-rays indicates that the interstellar protons have an average density around 100 cm$^{-3}$ and shows a good spatial correspondence with the TeV $\gamma$-rays. The total cosmic ray proton energy is estimated to be $\sim10^{48}$ erg for the hadronic $\gamma$-ray production, which may still be an underestimate by a factor of a few due to a small filling factor of the SNR volume by the interstellar protons. This result presents a third case, after RX J1713.7$-$3946 and HESS J1731$-$347, of the good spatial correspondence between the TeV $\gamma$-rays and the interstellar protons, lending further support for a hadronic component in the $\gamma$-rays from young TeV $\gamma$-ray SNRs., Comment: 22 pages, 2 tables, 14 figures, accepted for publication in The Astrophysical Journal (ApJ)

The nucleon-nucleon J-matrix Inverse Scattering Potential JISP16 is applied to elastic nucleon-deuteron (Nd) scattering and the deuteron breakup process at the lab. nucleon energies up to 135 MeV. The formalism of the Faddeev equations is used to obtain 3N scattering states. We compare predictions based on the JISP16 force with data and with results based on various NN interactions: the CD Bonn, the AV18, the chiral force with the semi-local regularization at the 5th order of the chiral expansion and with low-momentum interactions obtained from the CD Bonn force as well as with the predictions from the combination of the AV18 NN interaction and the Urbana IX 3N force. JISP16 provides a satisfactory description of some observables at low energies but strong deviations from data as well as from standard and chiral potential predictions with increasing energy. However, there are also polarization observables at low energies for which the JISP16 predictions differ from those based on the other forces by a factor of two. The reason for such a behavior can be traced back to the P-wave components of the JISP16 force. At higher energies the deviations can be enhanced by an interference with higher partial waves and by the properties of the JISP16 deuteron wave function. In addition, we compare the energy and angular dependence of predictions based on the JISP16 force with the results of the low-momentum forces obtained with different values of the momentum cutoff parameter. We found that such low-momentum forces can be employed to interpret the Nd elastic scattering data only below some specific energy which depends on the cutoff parameter. Since JISP16 is defined in a finite oscillator basis, it has properties similar to low momentum interactions and its application to the description of Nd scattering data is limited to a low momentum transfer region., Comment: 26 pages, 12 eps figures; Version accepted to Phys. Rev. C: text is shortened, few figures regarding the nucleon-deuteron elastic scattering observables are removed but a short discussion of the nucleon induced deuteron breakup cross section is added. Conclusions remain unchanged

Dark gas in the interstellar medium (ISM) is believed to not be detectable either in CO or Hi radio emission, but it is detected by other means including gamma-rays, dust emission and extinction traced outside the Galactic plane at |b|>5 degree. In these analyses, the 21-cm HI emission is usually assumed to be completely optically thin. We have reanalyzed the HI emission from the whole sky at |b|>15 degree by considering temperature stratification in the ISM inferred from the Planck/IRAS analysis of the dust properties. The results indicate that the HI emission is saturated with an optical depth ranging from 0.5 to 3 for 85% of the local HI gas. This optically thick HI is characterized by spin temperature in the range 10K-60K, significantly lower than previously postulated in the literature, whereas such low temperature is consistent with emission/absorption measurements of the cool HI toward radio continuum sources. The distribution and the column density of the HI are consistent with those of the dark gas sug- gested by gamma-rays, and it is possible that the dark gas in the Galaxy is dominated by optically thick cold HI gas. This result implies that the average density of HI is 2-2.5 times higher than that derived on the optically-thin assumption in the local ISM., Comment: 45 pages, 17 figures, 3 tables, Accepted for publications in ApJ

We have discovered two molecular features at radial velocities of -35 km/s and 0 km/s toward the infrared Double Helix Nebula (DHN) in the Galactic center with NANTEN2. The two features show good spatial correspondence with the DHN. We have also found two elongated molecular ridges at these two velocities distributed vertically to the Galactic plane over 0.8 degree. The two ridges are linked by broad features in velocity and are likely connected physically with each other. The ratio between the 12CO J=2-1 and J=1-0 transitions is 0.8 in the ridges which is larger than the average value 0.5 in the foreground gas, suggesting the two ridges are in the Galactic center. An examination of the K band extinction reveals a good coincidence with the CO 0 km/s ridge and is consistent with a distance of 8 +/-2 kpc. We discuss the possibility that the DHN was created by a magnetic phenomenon incorporating torsional Alfv\'en waves launched from the circumnuclear disk (Morris, Uchida & Do 2006) and present a first estimate of the mass and energy involved in the DHN., Comment: 32 pages, 23 figures, Accepted by ApJ

The reformulated coupled-cluster method (CCM), in which average many-body potentials are introduced, provides a useful framework to organize numerous terms appearing in CCM equations, which enables us to clarify the structure of the CCM theory and physical importance of various terms more easily. We explicitly apply this framework to $^4$He, retaining one-body and two-body correlations as the first illustrating attempt. Numerical results with using two modern nucleon-nucleon interactions (AV18 and CD-Bonn) and their low-momentum interactions are presented. The characters of short-range and many-body correlations are discussed. Although not considered explicitly, the expression of the ground-state energy in the presence of a three-nucleon force is given., Comment: 12 pages, 11 figures, accepted for publication in PRC

Introducing a new vertex function, Z(E), of an energy variable E, we derive a new equation for the effective interaction. The equation is obtained by replacing the Q-box in the Krenciglowa-Kuo (KK) method by Z(E). This new approach can be viewed as an extension of the KK method. We show that this equation can be solved both in iterative and non-iterative ways. We observe that the iteration procedure with Z(E) brings about fast convergence compared to the usual KK method. It is shown that, as in the KK approach, the procedure of calculating the effective interaction can be reduced to determining the true eigenvalues of the original Hamiltonian H and they can be obtained as the positions of intersections of graphs generated from Z(E). We find that this graphical method yields always precise results and reproduces any of the true eigenvalues of H. The calculation in the present approach can be made regardless of overlaps with the model space and energy differences between unperturbed energies and the eigenvalues of H. We find also that Z(E) is a well-behaved function of E and has no singularity. These characteristics of the present approach ensure stability in actual calculations and would be helpful to resolve some difficulties due to the presence of poles in the Q-box. Performing test calculations we verify numerically theoretical predictions made in the present approach., Comment: 10 pages, 3 figures

A new method is given for the model-space effective interaction. Introducing a new operator in place of the Q-box in the Krenciglowa-Kuo (KK) method, we derive a new equation for the effective interaction. This equation can be viewed as an extension of the KK method. We show that this equation can be solved both in iterative and non-iterative ways. We observe that the iteration procedure brings about fast acceleration of convergence compared to the KK approach. We also find that the non-iterative calculation reproduces successfully any set of the true eigenvalues of the original Hamiltonian. This non-iterative calculation can be made regardless of the magnitudes of the overlaps with the model space and the energy differences between the unperturbed energy and the eigenvalues to be solved., Comment: 6 pages, 2 figures, 1 table, talk presented at 10th International Spring Seminar on Nuclear Physics "New Quests in Nuclear Structure", Vietri sul Mare, may 21-25, 2010. To be published on Journal of Physics Conference Series. Fig.1 and Fig.2 replaced. Content unchanged

We perform ab initio calculations for nuclei around ^{16}O, ^{40}Ca, and ^{56}Ni using realistic nucleon-nucleon forces. In particular, ^{56}Ni is computed as the heaviest nucleus in this kind of ab initio calculation. Ground-state and single-particle energies including three-body-cluster effects are obtained within the framework of the unitary-model-operator approach. It is shown that the CD-Bonn nucleon-nucleon potential gives quite good results close to the experimental values for all nuclei in the present work., Comment: 4 pages, 4 figures; accepted for publication in Physical Review Letters

Equivalent interactions in a low-momentum space for the $\Lambda N$, $\Sigma N$ and $\Xi N$ interactions are calculated, using the SU$_6$ quark model potential as well as the Nijmegen OBEP model as the input bare interaction. Because the two-body scattering data has not been accumulated sufficiently to determine the hyperon-nucleon interactions unambiguously, the construction of the potential even in low-energy regions has to rely on a theoretical model. The equivalent interaction after removing high-momentum components is still model dependent. Because this model dependence reflects the character of the underlying potential model, it is instructive for better understanding of baryon-baryon interactions in the strangeness sector to study the low-momentum space $YN$ interactions., Comment: 9 pages, 13 figures, accepted for publication in Phys. Rev. C

A realistic nucleon-nucleon potential is transformed into a low-momentum effective one (LMNN) using the Okubo theory. The separable potentials are converted from the LMNN with a universal separable expansion method and a simple Legendre expansion. Through the calculation of the triton binding energies, the separability for the convergence of these ranks is evaluated. It is found that there is a tendency for the lower momentum cutoff parameter $\Lambda$ of LMNN to gain good separability., Comment: 6 pages, 1 table

Microscopic nuclear structure calculations have been performed within the framework of the unitary-model-operator approach. Ground-state and single-particle energies are calculated for nuclei around ^{14}C, ^{16}O and ^{40}Ca with modern nucleon-nucleon interactions., Comment: 6 pages, 4 figures, Talk presented at the International Symposium on Correlation Dynamics in Nuclei (CDN05), Jan. 1 - Feb. 4, 2005, Tokyo, Japan

A general definition of the model-space effective interaction is given. The energy-independent effective hamiltonians derived in a time-independent way are classified systematically., Comment: To appear in IJMPE; Proceedings of "Blueprints for the Nucleus," Istanbul, Turkey, May 2004

Binding energies of ^{3}H, ^{4}He, and ^{16}O are calculated, using low-momentum nucleon-nucleon interactions (V_{low-k}) for a wide range of the cutoff momentum \Lambda. In addition, single-particle energies in nuclei around ^{16}O are computed. The dependence of the binding energies and the single-particle energies in these nuclei on the cutoff momentum \Lambda of the V_{low-k} is examined. Furthermore, the availability of the V_{low-k} in nuclear structure calculations is discussed., Comment: 8 pages, 3 figures, Talk presented at the 8th International Spring Seminar on Nuclear Physics on Key Topics in Nuclear Structure

Low-momentum nucleon-nucleon interactions are derived within the framework of a unitary-transformation theory, starting with realistic nucleon-nucleon interactions. A cutoff momentum Lambda is introduced to specify a border between the low- and high-momentum spaces. By the Faddeev-Yakubovsky calculations the low-momentum interactions are investigated with respect to the dependence of ground-state energies of ^3H and ^4He on the parameter Lambda. It is found that we need the momentum cutoff parameter Lambda >= 5 fm^-1 in order to reproduce satisfactorily the exact values of the binding energies for ^3H and ^4He. The calculation with Lambda =2 fm^-1 recommended by Bogner et al. leads to considerable overbinding at least for the few-nucleon systems., Comment: 9 pages, 10 figures, 1 table

Shell structures in the N\simeq Z nucleus ^{17}O and the neutron-rich oxygen isotopes ^{23}O and ^{25}O are microscopically described by calculating single-particle energies with modern nucleon-nucleon interactions within the framework of the unitary-model-operator approach. It is found that the effect of three-body cluster terms on the single-particle energy is more important in ^{23}O and ^{25}O than ^{17}O., Comment: 5 pages, 1 figure, Talk at the International Symposium on "A New Era of Nuclear Structure Physics (NENS03)", 19-22 Nov. 2003, Niigata, Japan

The binding energies of the ground states and several excited states related to single-particle and -hole states in nuclei around ^{16}O are calculated taking charge dependence into account. Effective interactions on the particle basis are constructed from modern charge-dependent nucleon-nucleon interactions and the Coulomb force within the framework of the unitary-model-operator approach. Single-particle (-hole) energies are obtained from the energy differences of the binding energies between a particle (hole) state in ^{17}O or ^{17}F (^{15}N or ^{15}O) and the ground state of ^{16}O. The resultant spin-orbit splittings are small for the hole state and large for the particle state in comparison with the experimental values though the differences between the experimental and calculated values are not very large. The charge dependence of the calculated single-particle energies for the ground states are in good agreement with the experimental values. Furthermore, the Thomas-Ehrman shift due to the Coulomb force for the 1s_{1/2} states in ^{17}O and ^{17}F can be observed., Comment: 14 pages, 12 figures, submitted to Phys. Rev. C

Shell-model calculations in a large model space are performed for _{\Lambda}^{16}O and_{\Lambda}^{17}O. Effective interactions with degrees of freedom of \Sigma in addition to \Lambda and nucleons are derived from hyperon-nucleon and nucleon-nucleon interactions within the framework of the unitary-model-operator approach. Effects of the \Sigma degrees of freedom and the parity-mixing intershell coupling on the \Lambda hypernuclear structure are investigated, employing the Nijmegen NSC97a-f and NSC89 hyperon-nucleon potentials., Comment: 11 pages, 5 figures, submitted to Phys. Rev. C

A method for a microscopic description of Lambda hypernuclei is formulated in the framework of the unitary-model-operator approach. A unitarily transformed hamiltonian is introduced and given in a cluster expansion form. The structure of three-body-cluster terms are discussed especially on the Lambda single-particle energy. The Lambda single-particle energies including the three-body-cluster contributions are calculated for the 0s_{1/2}, 0p_{3/2} and 0p_{1/2} states in_{Lambda}^{17}O, and for the 0s_{1/2}, 0p_{3/2}, 0p_{1/2}, 0d_{5/2}, 0d_{3/2} and 1s_{1/2} states in_{Lambda}^{41}Ca, using the Nijmegen soft-core (NSC), NSC97a-f, the Juelich A (J A) and J B hyperon-nucleon interactions. It is indicated that the three-body-cluster terms bring about sizable effects in the magnitudes of the Lambda single-particle energies, but hardly affect the Lambda spin-orbit splittings., Comment: LaTeX 19 pages including 7 figures, ptptex.sty is used

Exact expressions of the Pauli exclusion operator Q in the nuclear matter calculation are presented in detail. Exact formulae are also given for the calculations of the single-particle-potential energy and the binding energy per nucleon with the exact Q operator. Numerical calculations of the G matrix in the lowest-order Brueckner theory are carried out to check the reliability of the standard angle-average approximation for the Q operator by employing the Bonn B and C NN potentials. It is observed that the exact treatment of the operator Q brings about non-negligible and attractive contributions to the binding energy., Comment: 16 pages, 3 figures

A method is formulated for the description of lambda hypernuclei in the framework of the unitary-model-operator approach (UMOA). The method is applied to $_{\Lambda}^{17}$O. A lambda-nucleon effective interaction is derived, taking the coupling of the sigma-nucleon channel into account. The lambda single-particle energies are calculated for the 0s_{1/2}, 0p_{3/2} and 0p_{1/2} states employing the Nijmegen soft-core (NSC), J\"ulich model-\~A (J\~A) and model-\~B (J\~B) hyperon-nucleon potentials., Comment: LaTeX, 27 pages, 4 figures, uses elsart.cls, submitted to Nucl. Phys. A, revised version, the words 'unitary-correlation-operator method' have been changed to 'unitary-model-operator approach' in order to avoid unnecessary confusion, and relevant sentences have been modified

The Hermitian effective interaction can be well-approximated by (R+R^dagger)/2 if the eigenvalues of omega^dagger omega are small or state-independent(degenerate), where R is the standard non-Hermitian effective interaction and omega maps the model-space states onto the excluded space. An error bound on this approximation is given., Comment: 13 pages

We generalize the Lee-Suzuki iteration method for summing the folded diagram series to the case where the unperturbed model-space energies are non-degenerate. A condition is derived for the convergence of the iteration scheme and this depends on the choice of the model space projection operators. Two choices are examined, in the first the projection operators are defined in terms of the unperturbed states and in the second they are defined in terms of the eigenfunctions obtained at each stage of the iteration. As is illustrated by calculations with a simple model, the second procedure gives the better convergence and, by suitable choice of the starting energies, allows the reproduction of any subset of the exact eigenvalues., Comment: Latex, 23 pages, 4 figures (postscript, available from authors), Minnesota preprint NUC-MINN-93/11-T