Cosmic Microwave Background Radiation Anisotropy Induced by Cosmic Strings

We report on a current investigation of the anisotropy pattern induced by cosmic strings on the cosmic microwave background radiation (MBR). We have numerically evolved a network of cosmic strings from a redshift of $Z = 100$ to the present and calculated the anisotropies which they induce. Based on a limited number of realizations, we have compared the results of our simulations with the observations of the COBE-DMR experiment. We have obtained a preliminary estimate of the string mass-per-unit-length $\mu$ in the cosmic string scenario.Comment: 8 pages of TeX - [Color] Postscript available by anonymous ftp at ftp://fnas08.fnal.gov:/pub/Publications/Conf-94-197-A, FERMILAB-Conf-94/197-

Core based tree multicast (M-CBT) approach in supporting mobility

IP multicasting provides a mechanism for faster handoff support than Mobile IP. Coupled with its location independent addressing, multicasting is a viable alternative to support mobility in the Internet. This paper continues research into using IP multicasting in mobility. Our proposed scheme looks at enabling a mobile node to initiate two way communications with a corresponding node on a shared multicast tree. We use as much of the existing Internet architecture as possible by making the base station a member of the multicast group. The mobile is not directly connected to the tree but goes through the base station to send and receive packets. This paper explains the differences and advantages of our proposed scheme compared with other multicast based mobility schemes and Mobile IP

Performance of a shared tree multicast label filter architecture

This paper defines a new multicast filter algorithm. This algorithm is used to filter packets on a mobile multicast architecture using a multicast shared tree. In a mobile multicast architecture, communications between a corresponding node (source) and the mobile node (receiver) should be private and not be sent to every node (receivers) on the multicast tree. We propose using an algorithm that sets up a label sub-tree on an existing mobile multicast shared tree to filter packets based on these labels. Our proposed label filter architecture is implemented differently to the current MPLS architecture. In this paper, we validate the effectiveness of the label filter in mobile communication compared to the traditional method of creating a new multicast tree by analysing the message and time complexity of the algorithm against the setting up time of a new multicast shared tree

Mobility and quality of service in wireless multicast infrastructure

This paper defines a new wireless mobility architecture with quality of service (QoS) that uses the fixed network infrastructure for group communication. The mobile core-based tree (M-CBT) architecture uses multicast to provide fast handoff and reduce network utilization costs for group communication. The M-CBT architecture can be coupled with a multicast QoS routing protocol to provide QoS for mobile communication. The Explore Best Path Message (EBPM) protocol is a probe-based dynamic distributed multicast QoS routing protocol that is designed to quickly search the network for an optimal QoS path from a joining node to the multicast tree. This paper illustrates how mobile devices using M-CBT and EBPM can participate in group communications and quickly find a QoS path as theyhandoff to a new network

Implementing label filters on a shared tree mobile multicast architecture

This paper describes an architecture that filters packets within a subset of nodes on an existing shared multicast tree. The path connecting the group of nodes that want to communicate privately on the existing tree was given a label. These labels are used to route one-to-one and group communication traffic for selected nodes on a multicast tree. Nodes connected to the tree but are not on this label path do not receive any filtered packets. This filter architecture reduces network resource waste by utilising the existing network resources on the multicast tree like quality of service (QoS). In this paper, we also describe how this architecture can be used for mobile communication when implemented in a shared tree mobile multicast architecture

Real-time public group collaboration using IP multicast label filters

Internet based enterprise level collaboration tools enable organizations to make decisions faster and more accurately with less effort. However, these tools provide limited real-time group collaboration within and across organizations. Multicast protocols were developed to provide efficient group communication. This paper proposes a novel IP multicast network layer filter architecture that provides efficient and scalable real-time group collaboration between the required entities within an organization. This proposed network architecture uses a label filter mechanism to improve scalability and bandwidth for one-to-many and many-to-many real-time collaboration

Large Angular Scale CMB Anisotropy Induced by Cosmic Strings

We simulate the anisotropy in the cosmic microwave background (CMB) induced by cosmic strings. By numerically evolving a network of cosmic strings we generate full-sky CMB temperature anisotropy maps. Based on $192$ maps, we compute the anisotropy power spectrum for multipole moments $\ell \le 20$. By comparing with the observed temperature anisotropy, we set the normalization for the cosmic string mass-per-unit-length $\mu$, obtaining $G\mu/c^2=1.05 {}^{+0.35}_{-0.20} \times10^{-6}$, which is consistent with all other observational constraints on cosmic strings. We demonstrate that the anisotropy pattern is consistent with a Gaussian random field on large angular scales.Comment: 4 pages, RevTeX, two postscript files, also available at http://www.damtp.cam.ac.uk/user/defects/ to appear in Physical Review Letters, 23 September 199

The growth of linear perturbations in generic defect models for structure formation

We study the growth of linear perturbations induced by a generic causal scaling source as a function of the cosmological parameters $h$, $\Omega^m_0$ and $\Omega^\Lambda_0$. We show that for wavenumbers k \gsim 0.01 h/Mpc the spectrum of density and velocity perturbations scale in a similar way to that found in inflationary models with primordial perturbations. We show that this result is independent of the more or less incoherent nature of the source, the small scale power spectrum of the source and of deviations from scaling which naturally occur at late times if $\Omega^m_0 \neq 1$.Comment: 4 pages, 2 figure

Nil Intervention is at Times the Best Intervention: Benign emptying of pneumonectomy space

A sudden drop of air-fluid level in the pneumonectomy space in the absence of a bronchopleural fistula and pleural infection is termed benign emptying of the post pneumonectomy space (BEPS). We herein report a case of benign emptying of pneumonectomy space, briefly review the literature and enumerate possible mechanisms for the same. It is an extremely rare entity and follows a benign course. Patients with BEPS are clinically stable, afebrile with no fluid expectoration, and have a normal white blood cell count. Bronchoscopy reveals an intact bronchial stump and pleural fluid cultures are often sterile. Close monitoring and early detection of a bronchopleural fistula is the management. Clinicians should keep BEPS among the differential diagnosis in case of a drop in the air-fluid level of the post pneumonectomy space. Awareness of this entity is crucial as it helps prevent unnecessary and morbid surgical interventions. Keywords: Pneumonectomy; BEPS; Bronchopleural Fistula; India