M2-M5 Systems in N=6 Chern-Simons Theory

We study two aspects of M5-branes in N=6 U(N)xU(N) Chern-Simons gauge theory. We first examine multiple M2-branes ending on a M5-brane. We study Basu-Harvey type cubic equations, fuzzy funnel configurations, and derive the M5-brane tension from the N=6 theory. We also find a limit in which the above M2-M5 system reduces to a D2-D4 system and we recover the Nahm equation from the N=6 theory. We then examine domain wall configurations in mass-deformed N=6 theory with a manifest SU(2)xSU(2)xU(1) global symmetry. We derive tensions of domain walls connecting between arbitrary M5-brane vacua of the deformed theory and observe their consistency with gravity dual expectations.Comment: 15 pages, Latex. v2: typos fixed, reference added. v3: Journal version in JHE

Light Gauginos and Conformal Sequestering

In a wide class of direct and semi-direct gauge mediation models, it has been observed that the gaugino masses vanish at leading order. It implies that there is a hierarchy between the gaugino and sfermion masses, invoking a fine-tuning problem in the Higgs sector via radiative corrections. In this paper, we explore the possibility of solving this anomalously light gaugino problem exploiting strong conformal dynamics in the hidden sector. With a mild assumption on the anomalous dimensions of the hidden sector operators, we show that the next to leading order contributions to the gaugino masses can naturally be in the same order as the sfermion masses. \mu/B_\mu problem is also discussed.Comment: 17 pages, 1 figure. References adde

Information Channels in Labor Markets. On the Resilience of Referral Hiring

Economists and sociologists disagree over markets' potential to assume functions typically performed by networks of personal connections, first among them the transmission of information. This paper begins from a model of labor markets where social ties are stronger between similar individuals and firms employing productive workers prefer to rely on personal referrals than to hire on the anonymous market (Montgomery (1991). However, we allow workers in the market to engage in a costly action that can signal their high productivity, and ask whether the possibility of signaling reduces the reliance on the network. We find that the network is remarkably resilient. To be effective signaling must fulfill two contradictory requirements: unless the signal is extremely precise, it must be expensive or it is not informative; but it must be cheap, or the network can undercut it.Networks, Signaling, Referral hiring, Referral premium

Marriage relationships among households in the mid 19th century Tama, Japan

This paper studies the formation of marriage relationships between two households in 19th century, Tama, Japan. Previous studies on marriage market or partner selection in the Japanese past tended to rely either on information from a single village in case of statistical analysis, or on collection of oral histories. By using the information from a household register that covers 35 villages, and applying the method of social network analysis, this paper goes beyond the limitation of previous studies. Our empirical results show that there was a tendency for socio-economic homogamy and endogamy (within kinship and within village) among peasants in the mid 19th century Tama, Japan.Marriage, Japan, Network, Household, Household registers

Marriage Relationships Among Households in the mid 19th Century Tama, Japan

This paper studies the formation of marriage relationships between two households in 19th century, Tama, Japan. Previous studies on marriage market or partner selection in the Japanese past tended to rely either on information from a single village in case of statistical analysis, or on collection of oral histories. By using the information from a household register that covers 35 villages, and applying the method of social network analysis, this paper goes beyond the limitation of previous studies. Our empirical results show that there was a tendency for socio-economic homogamy and endogamy (within kinship and within village) among peasants in the mid 19th century Tama, Japan.

Firm Structure, Search and Environmental Complexity

In this paper we explore the information processing problem of the firm by modeling the firm as type of network, which is comprised of two kinds of agents, 'searchers' and 'managers.' The searchers explore the external environment and report the information to the managers. We explore the role of centralization/decentralization in organizational structure to see how it affects firm performance. Centralization is defined in terms of the level at which decisions are made. We assume the information processing organization is arranged hierarchically, but that decisions can be made at different levels, and thus centralization directly relates to the quantity of information used in making a decision. We model the external environment as an NK landscape. Via simulations, we explore which type of organizational structure and level of decision making maximizes firm profits, given the complexity of the environmentOrganizational Structure, Decentralization, NK Landscape, Firm Search

Characterization of Balanced Coherent Configurations

Let $G$ be a group acting on a finite set $\Omega$. Then $G$ acts on $\Omega\times \Omega$ by its entry-wise action and its orbits form the basis relations of a coherent configuration (or shortly scheme). Our concern is to consider what follows from the assumption that the number of orbits of $G$ on $\Omega_i\times \Omega_j$ is constant whenever $\Omega_i$ and $\Omega_j$ are orbits of $G$ on $\Omega$. One can conclude from the assumption that the actions of $G$ on ${\Omega_i}$'s have the same permutation character and are not necessarily equivalent. From this viewpoint one may ask how many inequivalent actions of a given group with the same permutation character there exist. In this article we will approach to this question by a purely combinatorial method in terms of schemes and investigate the following topics: (i) balanced schemes and their central primitive idempotents, (ii) characterization of reduced balanced schemes

Complexity, Uncertainty, and Organizational Congruency

Many scholars in the fields of organization theory and management strategy have argued that there is a tension between the two types of organizational learning activities, exploration and exploitation. They appear to be substitutes: the greater the skill at one, the harder it is to do the other well. It is often argued that the two activities compete for scarce resources when firms need different capabilities and management policies to promote one over the other. We present another explanation that attributes the phenomenon to the dynamic interactions among the activities, search, knowledge sharing, evaluation, and alignment within organizations relying on the NK Landscape framework (Kauffman 1993). Our results show that successful organizations tend to bifurcate into two types: those that always promote individual initiatives and build organizational strengths on individual learning and those good at aligning the individual knowledge base and exploiting shared knowledge. Straddling between the two types often fails. The intuition is that an equal mixture of individual search and organizational alignment slows down individual learning compared to the first orga nization type while making it difficult to update institutionalized knowledge because individuals' knowledge base is not so sufficiently aligned as in the second type. In such gstraddlingh organizations, once individuals get stuck with locally-best solutions in an uncoordinated manner, they cannot agree on how to improve the organizational knowledge. Straddling is especially inefficient when the operation is sufficiently complex (in other words, the interdependency is high) or when the business environment is sufficiently uncertain.