Density and Spin Linear Response of Atomic Fermi Superfluids with Population Imbalance in BCS-BEC Crossover

We present a theoretical study of the density and spin (representing the two components) linear response of Fermi superfluids with tunable attractive interactions and population imbalance. In both linear response theories, we find that the fluctuations of the order parameter must be treated on equal footing with the gauge transformations associated with the symmetries of the Hamiltonian so that important constraints including various sum rules can be satisfied. Both theories can be applied to the whole BCS-Bose-Einstein condensation crossover. The spin linear responses are qualitatively different with and without population imbalance because collective-mode effects from the fluctuations of the order parameter survive in the presence of population imbalance, even though the associated symmetry is not broken by the order parameter. Since a polarized superfluid becomes unstable at low temperatures in the weak and intermediate coupling regimes, we found that the density and spin susceptibilities diverge as the system approaches the unstable regime, but the emergence of phase separation preempts the divergence.Comment: 15 pages, 5 figure

Normative Legitimacy in the Commercialization of Online Community Website

Many online community websites start their operation by a not-for-profit business model, which attracts a lot of users to engage in. The huge user base and heavy Internet traffic could generate revenue and wealth for the websites. When the online communities are becoming popular, entrepreneurs of the online community website may hope to commercialize the online community. Nevertheless, some of community participants are against the commercialization of the online community website, since they regard that the property of online community is belonged to users rather than website owners. Users may challenge the legitimacy in the commercialization process of online community, and argue that the online community should be owned by the public rather than by a company since the enormous community participants put effort in it and make the website a popular one. This study used two case studies of online communities to explain the normative legitimate issues in the entrepreneurship of online community

BCS thermal vacuum of fermionic superfluids and its perturbation theory

The thermal field theory is applied to fermionic superfluids by doubling the degrees of freedom of the BCS theory. We construct the two-mode states and the corresponding Bogoliubov transformation to obtain the BCS thermal vacuum. The expectation values with respect to the BCS thermal vacuum produce the statistical average of the thermodynamic quantities. The BCS thermal vacuum allows a quantum-mechanical perturbation theory with the BCS theory serving as the unperturbed state. We evaluate the leading-order corrections to the order parameter and other physical quantities from the perturbation theory. A direct evaluation of the pairing correlation as a function of temperature shows the pseudogap phenomenon results from the perturbation theory. The BCS thermal vacuum is shown to be a generalized coherent and squeezed state. The correspondence between the thermal vacuum and purification of the density matrix allows a unitary transformation, and we found the geometric phase in the parameter space associated with the transformation.Comment: 14 pages, 2 figure

Maximizing Friend-Making Likelihood for Social Activity Organization

The social presence theory in social psychology suggests that computer-mediated online interactions are inferior to face-to-face, in-person interactions. In this paper, we consider the scenarios of organizing in person friend-making social activities via online social networks (OSNs) and formulate a new research problem, namely, Hop-bounded Maximum Group Friending (HMGF), by modeling both existing friendships and the likelihood of new friend making. To find a set of attendees for socialization activities, HMGF is unique and challenging due to the interplay of the group size, the constraint on existing friendships and the objective function on the likelihood of friend making. We prove that HMGF is NP-Hard, and no approximation algorithm exists unless P = NP. We then propose an error-bounded approximation algorithm to efficiently obtain the solutions very close to the optimal solutions. We conduct a user study to validate our problem formulation and per- form extensive experiments on real datasets to demonstrate the efficiency and effectiveness of our proposed algorithm

The Influence of the privacy concern and social advertising type on the attitude and behavior

Nowadays social media can collect consumers' online behavior. The enterprises make the customized advertisement to achieve targeting marketing and close consumers' needs. With the right of privacy, the consumers pay attention to this kind of advertisement. In this study, we made the online questionnaire. Asking the privacy concern, and analyzing the advertising attitude and behavior in a different advertising situation. The result we found that customized advertising made consumers increase positive attitude, but made negative attitude on advertising behavior like click, share, etc. In addition, both male and female have different responses to customized advertisements and intimate products advertisements. The result can serve a reference for manufacturers to make advertising strategies in the future

SELF-PRESENT BY AVATARS IN MULTIPLAYER ONLINE ROLE-PLAYING GAMES: THE INFLUENCE OF SELF-ESTEEM, ONLINE DISINHIBITION, AND SELF-DISCREPANCY

Playing Multiplayer Online Role-Playing Games (MMORPGs) is now a popular leisure activity for some people. Players spend significant energy and money on it. In MMORPGs, players can customize their avatars as virtual identities to present themselves in the virtual world. Avatars are important when playing MMORPGs. However, few previous studies focus on the psychological determinates for avatar presentation in MMORPGs. In this study, we used an online questionnaire of 337 participants to explore the antecedent factors influencing avatar presentation. The current study considers the influence of self-esteem, online disinhibition, and self-discrepancy on self-present and the influence of self-present on avatar presentation of idea self, stand out, and following a trend. The empirical survey result reveals the self-discrepancy between virtual and physical self are relative negatively with self-esteem and positive with online disinhibition. The self-present are influence by both self-discrepancy and online disinhibition. Besides, self-present perception will lead to avatar presentation. The current study provides contributions about confirming the antecedents of avatar presentation that may be serve as fundamental for future research on online game behavior

ALWAYS ON DUTY? THE POSITIVE AND NEGATIVE EFFECTS OF USING MOBILE SOCIAL NETWORKING TOOLS FOR WORK

The high penetration rate of mobile internet access makes the social networking tools ubiquitous. Through social networking tools, people now can easily contact others for social purpose as well as for work purpose. As a result, mobile social networking tools are now blurring the boundary between work and family domains and creating a new work-life relationship. Using social networking tools for work provides a lot of benefits as well as some negative effects. In the paper, we develop two empirical studies to examine both the positive effects and negative effects of using social networking tools for work. Our finding indicates that using social networking tools increases group effectiveness, which results in improvement of group identity. Nevertheless, using social networking tools for work also blurs the boundary of work-life, which may raise the work load and work-home conflict. We concluded that both academics and practice should pay attention to and minimize the negative impact of increased work overload and work-home conflict induced by using social networking tools for work. Our research results also provide suggestion for future research