Comments on Two-Loop Four-Particle Amplitude in Superstring Theory

It is shown that the four-particle amplitude of superstring theory at two loops obtained in [1,2] is equivalent to the previously obtained results in [3,4,5]. Here the ${\bf Z}_2$ symmetry in hyperelliptic Riemann surface plays an important role in the proof.Comment: 10 pages, Latex fil

Emergent Capabilities for Collaborative Teams in the Evolving Web Environment

This paper reports on our investigation of the latest advances for the Social Web, Web 2.0 and the Linked Data Web. These advances are discussed in terms of the latest capabilities that are available (or being made available) on the Web at the time of writing this paper. Such capabilities can be of significant benefit to teams, especially those comprised of multinational, geographically-dispersed team members. The specific context of coalition members in a rapidly formed diverse military context such as disaster relief or humanitarian aid is considered, where close working between non-government organisations and non-military teams will help to achieve results as quickly and efficiently as possible. The heterogeneity one finds in such teams, coupled with a lack of dedicated private network infrastructure, poses a number of challenges for collaboration, and the current paper represents an attempt to assess whether nascent Web-based capabilities can support such teams in terms of both their collaborative activities and their access to (and sharing of) information resources

Pairing Properties of Symmetric Nuclear Matter in Relativistic Mean Field Theory

The properties of pairing correlations in symmetric nuclear matter are studied in the relativistic mean field (RMF) theory with the effective interaction PK1. Considering well-known problem that the pairing gap at Fermi surface calculated with RMF effective interactions are three times larger than that with Gogny force, an effective factor in the particle-particle channel is introduced. For the RMF calculation with PK1, an effective factor 0.76 give a maximum pairing gap 3.2 MeV at Fermi momentum 0.9 fm$^{-1}$, which are consistent with the result with Gogny force.Comment: 14 pages, 6 figures

High Density Ratio Multi-Component Lattice Boltzmann Flow Model for Fluid Dynamics and CUDA Parallel Computation

The lattice Boltzmann equation (LBE) method is a promising technique for simulating fluid flows and modeling complex physics in fluids, and can be modified for solving general nonlinear partial differential equations (NPDEs). The LBE method has recently attracted more and more attention since it may help us to better understand the mechanisms of the complicated physical phenomena and dynamic processes modeled by NPDEs.In this dissertation, firstly, we developed a second-order accurate mass conserving boundary condition (BC) for the LBE method. Through several cases, the results show that our mass conserving BC will not result in the constant mass leakage that occurs for the other BCs in some cases. Additionally, it increases the efficiency and stability of the method for cases that involve relatively large magnitudes of body force.Secondly, we developed a multi-component and multi-phase LBE method for high density ratios. Multi-component multi-phase (MCMP) flow is very common in engineering or industrial problems and in nature. Because the lattice Boltzmann equation (LBE) model is based on microscopic models and mesoscopic kinetic equations, it offers many advantages for the study of multi-component or multi-phase flow problems. While the original formulation of Shan and Chen's(SC) model can incorporate some multiple phase and component scenarios, the density ratio of the different components is greatly restricted (less than approximately 2.0). This obviously limits the applications of this MCMP LBE model. Hence, based on the original SC MCMP model and the improvements in the single-component multi-phase (SCMP) flow model reported by Yuan and Schaefer, we have developed a new model that can simulate a MCMP system with a high density ratio.Finally, we developed a parallel computation LBE method based on Compute Unified Device Architecture (CUDA). CUDA offers a great economic alternative way to increase the calculation speed of LBE method instead of using a supercomputer. We present how to apply CUDA to the LBE method, including boundary condition treatments, single phase flow, thermal problems, and multi-phase cases. Through the results of several numerical experiments, our model with the help of CUDA can offer an improvement of a 10-30 times faster speed than that of a traditional single thread CPU code

A stereo vision technique based on the multi-positioned camera criterion

A modified feature based stereo vision [sic] technique is described in this thesis. The technique uses the curve-segments as the feature primitives in the matching process. The local characteristics of the curve-segments are extracted by the, Generalized Hough Transform. A set of images of a scene, which are taken by a multi-positioned camera satisfying the parallelism criterion, are first filtered by the Laplacian of a Gaussian operator in different widths, i.e. coarse to fine channels. At each channel, the Generalized Hough Transform is applied to the curve-segments in each image. The curve position, the curve-length, the curve centroid, the average gradient of the curve-segment and the R-table are, used as the local features in representing the distinctive characteristics of the curve-segment. These features of all the curve-segments, in an image are used as the constraints to find the corresponding curve-segments in the different images. The epipolar constraint oil the centroid of the curve-segment is used to limit the search window ill the images. Since the multi-images of one view are used, there exist more information about the scene than the two relational images criterion. Its performance compares to the other matching techniques, for example, the point, matching or twin image matching that the mismatching and the calculation are greatly reduced. Although the algorithm is not feasible for the realization of the real-time implementation of stereo vision [sic], it is a more economic way of finding the depth of all object or a view

Bivalence: Open Future or Logical Fatalism?

It is highly intuitive that the future is open in the sense that there are multiple possibilities for the future to obtain and we can determine how tomorrow is. For instance, it is possible that I will eat salad for lunch tomorrow, but it is also possible that I will eat food other than salad for lunch tomorrow. Suppose I eat salad finally. However, an argument of fatalism shows that the future is closed in the sense of being determined to be a certain way, and that whatever I do now, my eating salad tomorrow is inevitable. Fatalism calls into question the open future thesis, challenging theories of free will and moral responsibility. As the fatalist argument relies on the principle of bivalence, some proponents of the open future thesis refute fatalism by rejecting bivalence. In this paper, I argue that we need not reject bivalence to defend the open future thesis because bivalence is not sufficient evidence for fatalism, and another premise of the fatalist argument is problematic. I will show that bivalence is a neutral concept applicable to both theories of the future and does not commit us to fatalism. My argument does not privilege one theory over another. Instead, it simply elucidates the relationships between bivalence, the open future thesis, and fatalism. All of my work is based on the divergence between Markosian and Barnes and Cameron.In Section 1, I introduce the debate between fatalism and the open future thesis before detailing the traditional bivalence-based fatalist argument and demonstrating the centrality of bivalence to the debate in Section 2. In Section 3, I introduce some responses to fatalism, arguing that they are all flawed, which leads to my proposal, in Section 4, that the fatalist argument looks convincing because theorists do not recognize or understand the multiple significations of the term “future.” I then distinguish two distinct uses of “future” (real future and relative future) thereby disconnecting fatalism from bivalence and rendering bivalence compatible with the open future thesis. Finally, in Section 5, I take a broad view to conclude my proposal