Superfluid Fermi atomic gas as a quantum simulator for the study of neutron-star equation of state

We theoretically propose an idea to use an ultracold Fermi gas as a quantum simulator for the study of the neutron-star equation of state (EoS) in the low-density region. Our idea is different from the standard quantum simulator that heads for {\it perfect} replication of another system, such as a Hubbard model discussed in high-$T_{\rm c}$ cuprates. Instead, we use the {\it similarity} between two systems, and theoretically make up for the difference between them. That is, (1) we first show that the strong-coupling theory developed by Nozi\`eres-Schmitt Rink (NSR) can quantitatively explain the recent EoS experiment on a $^6$Li superfluid Fermi gas in the BCS (Bardeen-Cooper-Schrieffer)-unitary limit far below the superfluid phase transition temperature $T_{\rm c}$. This region is considered to be very similar to the low density region (crust regime) of a neutron star (where a nearly unitary $s$-wave neutron superfluid is expected). (2) We then theoretically compensate the difference that, while the effective range $r_{\rm eff}$ is negligibly small in a superfluid $^6$Li Fermi gas, it cannot be ignored ($r_{\rm eff}=2.7$ fm) in a neutron star, by extending the NSR theory to include effects of $r_{\rm eff}$. The calculated EoS when $r_{\rm eff}=2.7$ fm is shown to agree well with the previous neutron-star EoS in the low density region predicted in nuclear physics. Our idea indicates that an ultracold atomic gas may more flexibly be used as a quantum simulator for the study of other complicated quantum many-body systems, when we use, not only the experimental high tunability, but also the recent theoretical development in this field. Since it is difficult to directly observe a neutron-star interior, our idea would provide a useful approach to the exploration for this mysterious astronomical object.Comment: 29 pages, 7 figure

Worker discontent, voice, and EI programs in Japan: Evidence from the Japanese worker representation and participation survey

Using a unique new survey, the Japanese Worker Representation and Participation Survey (JWRPS), this paper documents that there is currently an alarming degree of worker discontent in Japan. Specifically, we find that: (i) nearly one in two Japanese workers usually do not look forward to going to work; (ii) almost one third of Japanese workers are dissatisfied with their current jobs and do not at all feel loyal to their employers or feel loyal only a little; (iii) nearly one in five Japanese workers either do not at all trust information provided by their firm or trust such information only a little; and (iv) fully 40 percent of Japanese workers rate labor management relations as only fair or poor. Estimating probit models, we find systematic evidence that such worker discontent is significantly related to the lack of strong employee voice on decisions affecting workplaces, and that the lack of or weakened use of Japan's once celebrated EI programs (such as Shopfloor Committees, Small Group Activities, and Joint Labor-Management Committees) is in part responsible for weak voice and hence an alarming degree of worker discontent. An important policy implication of our findings is that weakening Japan's participatory employment system (as the popular rhetoric at times suggests) may result in exacerbating the already alarming degree of worker discontent in Japan, and ultimately weakening the competitiveness of the Japanese economy

High Performance Work Practices and Employee Voice: A Comparison of Japanese and Korean Workers

Using a unique new cross-national survey of Japanese and Korean workers, we report the first systematic evidence on the effects on employee voice of High Performance Work Practices (HPWPs) from the two economies which are noted for the wide use of HPWPs. We find for both nations that: (i) workers in firms with HPWPs aimed at creating opportunities for employees to get involved (such as shopfloor committees and small group activities) are indeed more likely to have stronger senses of influence and voice on shopfloor decision making than other workers; (ii) workers whose pay is tied to firm performance are more likely to have a stake in firm performance and hence demand such influence and voice; and (iii) consequently workers in firms with HPWPs are more likely to make frequent suggestions for productivity increase and quality improvement. As such, this paper contributes to a small yet growing new empirical literature which tries to understand the actual process and mechanism through which HPWPs lead to better enterprise performance.high performance work practices, employee voice, Japan, Korea