Topics in double field theory

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 199-204).The existence of momentum and winding modes of closed string on a torus leads to a natural idea that the field theoretical approach of string theory should involve winding type coordinates as well as the usual space-time coordinates. Recently developed double field theory is motivated from this idea and it implements T-duality manifestly by doubling the coordinates. In this thesis we will mainly focus on the double field theory formulation of different string theories in its low energy limit: bosonic, heterotic, type II and its massive extensions, and M = 1 super-gravity theory. In chapter 2 of the thesis we study the equivalence of different formulations of double field theory. There are three different formulations of double field theory: background field E formulation, generalized metric H formulation, and frame field EAM formulation. Starting from the frame field formalism and choosing an appropriate gauge, the equivalence of the three formulations of bosonic theory are explicitly verified. In chapter 3 we construct the double field theory formulation of heterotic strings. The global symmetry enlarges to O(D, D + n) for heterotic strings and the enlarged generalized metric features this symmetry. The structural form of bosonic theory can directly be applied to the heterotic theory with the enlarged generalized metric. In chapter 4 we develop a unified framework of double field theory for type II theories. The Ramond-Ramond potentials fit into spinor representations of the duality group 0(D, D) and the theory displays Spin+(D, D) symmetry with its self-duality relation. For a specific form of RR 1-form the theory reduces to the massive deformation of type IIA theory due to Romans. In chapter 5 we formulate the K = 1 supersymmetric extension of double field theory including the coupling to n abelian vector multiplets. This theory features a local 0(1, 9 + n) x 0(1, 9) tangent space symmetry under which the fermions transform.by Seung Ki Kwak.Ph.D

Institutional theory of naive money

Thesis: Ph. D., Massachusetts Institute of Technology, Sloan School of Management, 2018.Cataloged from PDF version of thesis.Includes bibliographical references.In the first chapter, I propose a theoretical framework to elucidate how capital from unsophisticated investors (naive money) is associated with fund performance dynamics. In the framework, when naive money invested in a fund exceeds the ideal amount for the manager's skill, it leads funds to under-perform persistently. In contrast, the model predicts that, when the amount of invested naive money is smaller than the ideal size of a fund reflecting the manager's skill, the fund performs the same as the market on a risk-adjusted basis. Empirical results using mutual fund data support this prediction. In the second chapter, I develop a model that characterizes how naive money influences the decisions of active mutual fund managers: in particular, managerial effort, fees, marketing expenses, private benefit-seeking, and risk-taking. My model predicts that managers who receive a surplus of naive money are inclined to reduce their managerial effort, charge higher fees, allocate more resources towards marketing, and pursue their private benefit by sacrificing returns to investors. In addition, it also predicts that a manager is most likely to increase idiosyncratic risk when the amount of invested naive money gets closer to a certain size of the fund that reflects the manager's skill. In the third chapter, I build a model to study how naive money affects funds' survivorship and entry decisions. Sufficient capital provision from unsophisticated investors elongates the survival of unskilled managers. Competition among funds determines the industry equilibrium, and the equilibrium is affected by several key market conditions: the aggregate investment opportunities, the aggregate capital inflows from unsophisticated investors, and the supply of skilled managers. When AM markets are heterogeneous in investor sophistication, the model shows, AM markets with more sophisticated investors (say, hedge fund markets) differentiate from those with less sophisticated investors (say, mutual fund markets). Skilled managers generate more value in hedge fund markets, and choose to enter those markets.by Seung Ki Kwak.1. Theory and Evidence: Mutual Fund Performance Dynamics -- 2. IO of Active Mutual Funds -- 3. IO of the Active AM Industry: Entries and Exits.Ph. D

Unification of Type II Strings and T-duality

We present a unified description of the low-energy limits of type II string theories. This is achieved by a formulation that doubles the space-time coordinates in order to realize the T-duality group O(10,10) geometrically. The Ramond-Ramond fields are described by a spinor of O(10,10), which couples to the gravitational fields via the Spin(10,10) representative of the so-called generalized metric. This theory, which is supplemented by a T-duality covariant self-duality constraint, unifies the type II theories in that each of them is obtained for a particular subspace of the doubled space.Comment: 4 pages, v2: minor changes, to appear in PR

Психологическая готовность инвалидов к получению профессионального образования

Представленные результаты пилотажного исследования психологической готовности абитуриентов-инвалидов к получению профессионального образования получены на основе психолого-педагогического общения исследователей с группой молодых инвалидов-слушателей курса довузовской подготовки. Итоги исследования убеждают, что профессиональное образование является для инвалидов ведущей целью, с ним они связывают достижение наиболее важных жизненных целей, возможность самореализации в будущем

Invariances and Equations of Motion in Double Field Theory

We investigate the full set of equations of motion in double field theory and discuss their O(D,D) symmetry and gauge transformation properties. We obtain a Ricci-like tensor, its associated Bianchi identities, and relate our results to those with a generalized metric formulation.Comment: 24 page

The effect of palonosetron on rocuronium-induced withdrawal movement

AbstractBackgroundRocuronium causes pain and withdrawal movement during induction of anesthesia. In this study, palonosetron was investigated to have analgesic effect on the reduction of rocuronium-induced withdrawal movement.Methods120 patients were randomly assigned to one of three groups to receive either saline, lidocaine 20mg, or palonosetron 0.075mg with a tourniquet applied two minutes before thiopental sodium (5mg·kg−1) was given intravenously. After loss of consciousness, rocuronium (0.6mg·kg−1) was injected and the withdrawal movement was estimated by 4-point scale in a double-blind manner.ResultsThe overall incidence of rocuronium withdrawal movement was 50% with lidocaine (p=0.038), 38% with palonosetron (p=0.006) compared with 75% for saline. The incidence of no pain to mild pain was significantly lower in the lidocaine and palonosetron groups (85% and 92% respectively) than in the saline group (58%). However, there was no significant difference in withdrawal movement between the lidocaine and palonosetron groups. There was no severe movement with palonosetron.ConclusionPretreatment of palonosetron with venous occlusion may attenuate rocuronium-induced withdrawal movement as effective as the use of lidocaine. It suggested that peripheral action of palonosetron was effective to reduce rocuronium-induced withdrawal movement

Frame-like Geometry of Double Field Theory

We relate two formulations of the recently constructed double field theory to a frame-like geometrical formalism developed by Siegel. A self-contained presentation of this formalism is given, including a discussion of the constraints and its solutions, and of the resulting Riemann tensor, Ricci tensor and curvature scalar. This curvature scalar can be used to define an action, and it is shown that this action is equivalent to that of double field theory.Comment: 35 pages, v2: minor corrections, to appear in J. Phys.

Double Field Theory Formulation of Heterotic Strings

We extend the recently constructed double field theory formulation of the low-energy theory of the closed bosonic string to the heterotic string. The action can be written in terms of a generalized metric that is a covariant tensor under O(D,D+n), where n denotes the number of gauge vectors, and n additional coordinates are introduced together with a covariant constraint that locally removes these new coordinates. For the abelian subsector, the action takes the same structural form as for the bosonic string, but based on the enlarged generalized metric, thereby featuring a global O(D,D+n) symmetry. After turning on non-abelian gauge couplings, this global symmetry is broken, but the action can still be written in a fully O(D,D+n) covariant fashion, in analogy to similar constructions in gauged supergravities.Comment: 28 pages, v2: minor changes, version published in JHE

Ocular vestibular evoked myogenic potentials induced by air-conducted sound in patients with acute brainstem lesions

h i g h l i g h t s More than half of the patients with brainstem lesions showed abnormal air-conducted oVEMPs. The main lesion locations responsible for abnormal oVEMPs were the upper medial medulla, and the dorsomedial tegmentum of the pons and midbrain. Areas of the medial longitudinal fasciculus, the crossed ventral tegmental tracts and the oculomotor nucleus may carry the otolith-ocular signals required for oVEMP formation. a b s t r a c t Objective: The ocular vestibular-evoked myogenic potential (oVEMP), a recently documented otolithocular reflex, is considered to reflect the central projections of the primary otolithic afferent fibers to the oculomotor nuclei. The aim of our study is to define air-conducted sound oVEMP abnormality in patients with acute brainstem lesions and to determine the brainstem structures involved in the generation of oVEMPs. Methods: In response to air-conducted tone burst sounds (ACS), oVEMP was measured in 52 patients with acute brainstem lesions. Individualized brainstem lesions were analyzed by means of MRI-based voxel-wise lesion-behavior mapping, and the probabilistic lesion maps were constructed. Results: More than half (n = 28, 53.8%) of the patients with acute brainstem lesions showed abnormal oVEMP in response to ACS. The majority of patients with abnormal oVEMPs had lesions in the dorsomedial brainstem that contains the medial longitudinal fasciculus (MLF), the crossed ventral tegmental tract (CVTT), and the oculomotor nuclei and nerves. Conclusion: MLF, CVTT, and the oculomotor nuclei and nerves appear to be responsible for otolith-ocular responses in the brainstem. Significance: Complemented to cervical VEMP for the uncrossed otolith-spinal function, oVEMP to ACS may be applied to evaluate the crossed otolith-ocular function in central vestibulopathies

Massive Type II in Double Field Theory

We provide an extension of the recently constructed double field theory formulation of the low-energy limits of type II strings, in which the RR fields can depend simultaneously on the 10-dimensional space-time coordinates and linearly on the dual winding coordinates. For the special case that only the RR one-form of type IIA carries such a dependence, we obtain the massive deformation of type IIA supergravity due to Romans. For T-dual configurations we obtain a `massive' but non-covariant formulation of type IIB, in which the 10-dimensional diffeomorphism symmetry is deformed by the mass parameter.Comment: 21 page