4,516 research outputs found

    Quantum effects in the Alcubierre warp drive spacetime

    Get PDF
    The expectation value of the stress-energy tensor of a free conformally invariant scalar field is computed in a two-dimensional reduction of the Alcubierre ``warp drive'' spacetime. The stress-energy is found to diverge if the apparent velocity of the spaceship exceeds the speed of light. If such behavior occurs in four dimensions, then it appears implausible that ``warp drive'' behavior in a spacetime could be engineered, even by an arbitrarily advanced civilization.Comment: 9 pages, ReVTe

    Small Cells, Big Problems: The Increasing Precision of Cell Site Location Information and the Need for Fourth Amendment Protections

    Get PDF
    The past fifty years has witnessed an evolution in technology advancement in police surveillance. Today, one of the essential tools of police surveillance is something most Americans carry with them in their pockets every day, the cell phone. Cell phones not only contain a huge repository of personal data, they also provide continuous surveillance of a person’s movement known as cell site location information (CSLI). In 1986, Congress sought to provide some privacy protections to CSLI in the Stored Communication Act. Although this solution may have struck the proper balance in an age when cell phones were a mere novelty in the hands of a comparative few, we now live in an age where, as the U.S. Supreme Court recently recognized, cell phones could be seen “an important feature of human anatomy.” In 1986, there were only an estimated 681,825 subscribers serviced by 1531, cell sites. By 2013, there were 335 million subscribers and over 340,000 cell sites. Recently, cell phone service providers have begun to use small cell technologies, miniature cell phone towers that can provide additional coverage and bandwidth support to overburdened cellular networks. Small cells, known variously as femtocells, picocells, and microcells, are already installed throughout the United States, in particular in urban areas. As small cells overtake traditional cell phone towers as the most common means of transmitting cellular signals, CSLI will transform from a means of placing a person’s phone in a general area within a matter of miles to a precise location tracking tool charting a person’s movements down to a matter of feet. The late Justice Scalia in his 2001 majority opinion in Kyllo v. U.S., a case involving thermal imaging, opined that “while the technology used in the present case was relatively crude, the rule we adopt must take account of more sophisticated systems that are already in use or in development.” This Article explores the evolution of CSLI by focusing on the rise of small cell technologies. It also canvasses decisions in the circuits involving CSLI. It points out that the third-party exception to the Fourth Amendment is inapplicable to CSLI. Following Justice Scalia’s admonition, we believe that CSLI will only grow more precise as small cells infiltrate cellular networks and we therefore adopt an approach that incorporates the Fourth Amendment requirements for a search warrant particularly describing the place to be searched and items to be seized as well as the requirement for probable cause. Placing CSLI under the Fourth Amendment would make a major section of the Stored Communication Act unconstitutional

    Spatial Analysis of Rural Economic Development Using a Locally Weighted Regression Model

    Get PDF
    This study uses locally weighted regression to identify county-level characteristics that serve as drivers of creative employment throughout the southern United States. We found that higher per capita income, greater infrastructure investments, and the rural nature of a county tended to promote creative employment density, while higher scores on a natural amenity index had the opposite effect. We were also able to identify and map clusters of rural counties where the marginal effects of these variables on creative employment density were greatest. These findings should help rural communities to promote creative employment growth as a means of furthering rural economic development.creative class, locally weighted regression, natural amenities, rural economic development, Community/Rural/Urban Development,

    On the functions, mechanisms, and malfunctions of intracortical contextual modulation

    Get PDF
    A broad neuron-centric conception of contextual modulation is reviewed and re-assessed in the light of recent neurobiological studies of amplification, suppression, and synchronization. Behavioural and computational studies of perceptual and higher cognitive functions that depend on these processes are outlined, and evidence that those functions and their neuronal mechanisms are impaired in schizophrenia is summarized. Finally, we compare and assess the long-term biological functions of contextual modulation at the level of computational theory as formalized by the theories of coherent infomax and free energy reduction. We conclude that those theories, together with the many empirical findings reviewed, show how contextual modulation at the neuronal level enables the cortex to flexibly adapt the use of its knowledge to current circumstances by amplifying and grouping relevant activities and by suppressing irrelevant activities

    An All Optical Fibre Quantum Controlled-NOT Gate

    Full text link
    We report the first experimental demonstration of an optical controlled-NOT gate constructed entirely in fibre. We operate the gate using two heralded optical fibre single photon sources and find an average logical fidelity of 90% and an average process fidelity of 0.83<F<0.91. On the basis of a simple model we are able to conclude that imperfections are primarily due to the photon sources, meaning that the gate itself works with very high fidelity.Comment: 4 pages, 4 figures, comments welcom

    Evidence for Past Subduction Earthquakes at a Plate Boundary with Widespread Upper Plate Faulting: Southern Hikurangi Margin, New Zealand

    Get PDF
    At the southern Hikurangi margin, New Zealand, we use salt marsh stratigraphy, sedimentology, micropaleontology, and radiocarbon dating to document evidence of two earthquakes producing coseismic subsidence and (in one case) a tsunami over the past 1000 yrs. The earthquake at 520-470 yrs before present (B.P.) produced 0.25 +/- 0.1 m of subsidence at Big Lagoon. The earthquake at 880-800 yrs B.P. produced 0.45 +/- 0.1 m of subsidence at Big Lagoon and was accompanied by a tsunami that inundated >= 360 m inland with a probable height of >= 3.3 m. Distinguishing the effects of upper plate faulting from plate interface earthquakes is a significant challenge at this margin. We use correlation with regional upper plate paleoearthquake chronologies and elastic dislocation modeling to determine that the most likely cause of the subsidence and tsunami events is subduction interface rupture, although the older event may have been a synchronous subduction interface and upper plate fault rupture. The southern Hikurangi margin has had no significant (M > 6.5) documented subduction interface earthquakes in historic times, and previous assumptions that this margin segment is prone to rupture in large to great earthquakes were based on seismic and geodetic evidence of strong contemporary plate coupling. This is the first geologic evidence to confirm that the southern Hikurangi margin ruptures in large earthquakes. The relatively short-time interval between the two subduction earthquakes (similar to 350 yrs) is shorter than in current seismic-hazard models.GNSEQC Biennial ProjectNew Zealand Natural Hazards Research Platform and Foundation for Research Science and TechnologyInstitute for Geophysic

    Analysis of maritime support vessels and acquisition methods utilized to support maritime irregular warfare

    Get PDF
    MBA Professional ReportAs the U.S. military continuously aligns the appropriate platforms to conduct Maritime Irregular Warfare (MIW), Special Operations Command (SOCOM) has leased/chartered civilian ships to provide the appropriate vessels needed to support operations in Operation Enduring Freedom-Philippines (OEF-P). The framework of this study showcases three specific vessels with their corresponding capabilities on cost per day basis. Our findings and analyses may aid commanders in determining the most appropriate vessel and cost-effective acquisition method to accomplish specific MIW missions in not only OEF-P, but also in other MIW environments. Based on the analysis and recommendations presented in this project, decision makers in this arena will have a mechanism from which to make a more informed decision regarding the acquisition of vessels supporting MIW. Decision makers will be able to evaluate various potential MIW scenarios; identify specific vessel capabilities to meet their operational requirements; and acquire vessels more cost-effectively based on total daily rate costs.http://archive.org/details/analysisofmariti109451051
    • …
    corecore