727 research outputs found
Bonus scaling and BCFW in N=7 supergravity
In search of natural building blocks for supergravity amplitudes, a tentative
criteria is term-by-term bonus z^-2 large momentum scaling. For a given choice
of deformation legs, we present such an expansion in the form of a BCFW
representation in N=7 supergravity based on a special shift. We will show that
this improved scaling behavior, with respect to the fully N=8 representation,
is due to its automatic incorporation of the so called bonus relations.Comment: 16 pages, 2 figure
A Continuous Model of Multilateral Bargaining with Random Arrival Times
This paper proposes a continuous-time model framework of bargaining, which is analytically tractable even in complex situations like coalitional bargaining. The main ingredients of the model are: (i) players get to make offers according to a random arrival process; (ii) there is a deadline that ends negotiations. In the case of n-player group bargaining, there is a unique subgame-perfect Nash equilibrium, and the share of the surplus a player can expect is proportional to her arrival rate. In general coalitional bargaining, existence and uniqueness of Markov perfect equilibrium is established. In convex games, the set of limit payoffs as the deadline gets infinitely far away exactly corresponds to the core. The limit allocation selected from the core is determined by the relative arrival rates. As an application of the model, legislative bargaining with deadline is investigated.
The Computational Complexity of Quantum Determinants
In this work, we study the computational complexity of quantum determinants,
a -deformation of matrix permanents: Given a complex number on the unit
circle in the complex plane and an matrix , the -permanent of
is defined as where
is the inversion number of permutation in the symmetric group on
elements. The function family generalizes determinant and permanent, which
correspond to the cases and respectively.
For worst-case hardness, by Liouville's approximation theorem and facts from
algebraic number theory, we show that for primitive -th root of unity
for odd prime power , exactly computing -permanent is
-hard. This implies that an efficient algorithm for
computing -permanent results in a collapse of the polynomial hierarchy.
Next, we show that computing -permanent can be achieved using an oracle that
approximates to within a polynomial multiplicative error and a membership
oracle for a finite set of algebraic integers. From this, an efficient
approximation algorithm would also imply a collapse of the polynomial
hierarchy. By random self-reducibility, computing -permanent remains to be
hard for a wide range of distributions satisfying a property called the strong
autocorrelation property. Specifically, this is proved via a reduction from
-permanent to -permanent for points on the unit circle.
Since the family of permanent functions shares common algebraic structure,
various techniques developed for the hardness of permanent can be generalized
to -permanents
In Vitro Efficacy of Combined Macrophage-Mediated Plasmonic Photothermal Therapy and Chemotherapeutic Agents
Although both chemotherapy and hyperthermia therapy have their inherent advantages, the non-specific targeting of chemotherapy and ineffectiveness of hyperthermia therapy alone suggests a better method can be developed. To overcome this problem, the combined treatment of chemotherapeutic agents with plasmonic photothermal therapy (PPTT) is proposed. This is the first study to investigate the efficacy of combined chemotherapy and PPTT using monocytes as delivery vehicles for gold nanoshells. The results of this investigation shows that PPTT combined with cisplatin resulted in some degree of synergism while additive effects were observed for concurrent treatments of PPTT and doxorubicin and PPTT and bleomycin
Coordination-Free Equilibria in Cheap Talk Games
This paper characterizes generic equilibrium play in a multi-sender version of Crawford and Sobel\u27s (1982) cheap talk model, when robustness to a broad class of beliefs about noise in the senders\u27 observation of the state is required. Just like in the one-sender model, information transmission is partial, equilibria have an interval form, and they can be computed through a generalized version of Crawford and Sobels forward solution procedure. Fixing the senders\u27 biases, full revelation is not achievable even as the state space becomes large. Intuitive welfare predictions, such as the desirability of consulting senders with small and opposite biases, follow
The role of initial geometry in experimental models of wound closing
Wound healing assays are commonly used to study how populations of cells,
initialised on a two-dimensional surface, act to close an artificial wound
space. While real wounds have different shapes, standard wound healing assays
often deal with just one simple wound shape, and it is unclear whether varying
the wound shape might impact how we interpret results from these experiments.
In this work, we describe a new kind of wound healing assay, called a sticker
assay, that allows us to examine the role of wound shape in a series of wound
healing assays performed with fibroblast cells. In particular, we show how to
use the sticker assay to examine wound healing with square, circular and
triangular shaped wounds. We take a standard approach and report measurements
of the size of the wound as a function of time. This shows that the rate of
wound closure depends on the initial wound shape. This result is interesting
because the only aspect of the assay that we change is the initial wound shape,
and the reason for the different rate of wound closure is unclear. To provide
more insight into the experimental observations we describe our results
quantitatively by calibrating a mathematical model, describing the relevant
transport phenomena, to match our experimental data. Overall, our results
suggest that the rates of cell motility and cell proliferation from different
initial wound shapes are approximately the same, implying that the differences
we observe in the wound closure rate are consistent with a fairly typical
mathematical model of wound healing. Our results imply that parameter estimates
obtained from an experiment performed with one particular wound shape could be
used to describe an experiment performed with a different shape. This
fundamental result is important because this assumption is often invoked, but
never tested
The contribution of mobile telecommunication technology to sustainable development in selected countries in Africa
Thesis (S.M. in Engineering and Management, and, in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 143-150).While most of the world's population resides in countries that are wealthy or developing, the rest reside in low-income and least developed countries (LDCs), left behind and growing more disconnected. At the same time, mobile phones are widely adopted in these underdeveloped areas and demonstrate potential for economic development. However, technological innovation and policies have often addressed narrow dimensions of poverty and development. Sustainable development, on the other hand, assesses the welfare of a country in its entirety. This then begs the question of how mobile telephony technology, given its pervasiveness, can be beneficial on a systemic and sustainable level. This document presents evidence that mobile phones can contribute to sustainable development in several ways. The focus is on selected countries in the sub-Saharan Africa region: Kenya, Tanzania, Uganda, and Nigeria, each of which is categorized as a LDC. The Sustainable Development framework is used to analyze data from case studies and existing technology, institutional and policy trends in the mobile telecommunication industry. The evidence from literature demonstrates that mobile initiatives focused on niche areas, such as banking and health, have benefited on the community level and improved operations within firms. Mobile industry policies have created a healthy system of innovation in these countries. However, environmental development has been secondary or even ignored. Thus, the recommendations focus on prioritizing sustainability, specific policies continuing diffusion and adoption, technology transfer mechanisms, increased robustness in data-tracking and countering external economic shocks. The data presented is not meant to be comprehensive nor complete. Consequently, suggested future work addresses short-term, mid-term, and long-term strategies. Specific areas include examining causal linkages for mobile phone adoption, designing technology initiatives around sustainability goals, and drivers that facilitate technology transfer. Mobile telecommunication technology offers real opportunities for development and growth in Africa. If the focus of development shifts from mere economic growth to sustainable development, countries can not only transform their economic fortunes but also enhance the quality of their environment.by Alexander Shih.S.M.in Engineering and Management, and, in Technology and Polic
Matching, Marriage, and Children: Differences Across Sexual Orientations
There are many differences in behavior across couples of different sexual orientations—some well known, others not. We propose a model which explains differences in expected matching behavior, marriage rates, non-child-friendly activities, and fertility, based on different costs of procreation and complementarities between marriage and children. The model predicts that the biological traits of same-sex couples, unlike those of heterosexual couples, should not be correlated—holding constant other household production characteristics. In addition, the model predicts that heterosexuals have a higher probability of having children and getting married, and that childless heterosexuals are less likely to engage in behaviors not complementary with children than childless gays and lesbians. Using two nationally representative probability samples that self-identify sexual orientation, these predictions are confirmed
TPA3D: Triplane Attention for Fast Text-to-3D Generation
Due to the lack of large-scale text-3D correspondence data, recent text-to-3D
generation works mainly rely on utilizing 2D diffusion models for synthesizing
3D data. Since diffusion-based methods typically require significant
optimization time for both training and inference, the use of GAN-based models
would still be desirable for fast 3D generation. In this work, we propose
Triplane Attention for text-guided 3D generation (TPA3D), an end-to-end
trainable GAN-based deep learning model for fast text-to-3D generation. With
only 3D shape data and their rendered 2D images observed during training, our
TPA3D is designed to retrieve detailed visual descriptions for synthesizing the
corresponding 3D mesh data. This is achieved by the proposed attention
mechanisms on the extracted sentence and word-level text features. In our
experiments, we show that TPA3D generates high-quality 3D textured shapes
aligned with fine-grained descriptions, while impressive computation efficiency
can be observed
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