1,605,592 research outputs found

    Tension is Dimension

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    We propose a simple universal formula for the tension of a D-brane in terms of a regularized dimension of the associated conformal field theory statespace.Comment: 18 pages, harvmac (b), one ref added, one typo fixe

    Progressive damage in stitched composites: Static tensile tests and tension-tension fatigue

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    The paper describes progressive damage in static tensile tests and tension-tension fatigue in structurally stitched carbon/epoxy NCF composites, in comparison with their non-stitched counterparts. Analogies between damage development in quasi-static tension and tension-tension fatigue are analyzed and links between the damage initiation thresholds in quasi-static tests and fatigue life are established

    Fatigue Damage in Notched Composite Laminates Under Tension-Tension Cyclic Loads

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    The results are given of an investigation to determine the damage states which develop in graphite epoxy laminates with center holes due to tension-tension cyclic loads, to determine the influence of stacking sequence on the initiation and interaction of damage modes and the process of damage development, and to establish the relationships between the damage states and the strength, stiffness, and life of the laminates. Two quasi-isotropic laminates were selected to give different distributions of interlaminar stresses around the hole. The laminates were tested under cyclic loads (R=0.1, 10 Hz) at maximum stresses ranging between 60 and 95 percent of the notched tensile strength

    Visible Branes with Negative Tension in Heterotic M-Theory

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    It is shown that there exist large classes of BPS vacua in heterotic M-theory which have negative tension on the visible orbifold plane, positive tension on the hidden plane and positive tension, physical five-branes in the bulk space. Explicit examples of such vacua are presented. Furthermore, it is demonstrated that the ratio, beta/|alpha|, of the bulk five-brane tension to the visible plane tension can, for several large classes of such vacua, be made arbitrarily small. Hence, it is straightforward to find vacua with the properties required in the examples of the Ekpyrotic theory of cosmology - a visible brane with negative tension and beta/|alpha| small. This contradicts recent claims in the literature.Comment: 30 page

    Bouncing Negative-Tension Branes

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    Braneworlds, understood here as double domain wall spacetimes, can be described in terms of a linear harmonic function, with kinks at the locations of the boundary branes. In a dynamical setting, there is therefore the risk that the boundary brane of negative tension, at whose location the value of the harmonic function is always lowest, can encounter a zero of this harmonic function, corresponding to the formation of a singularity. We show that for certain types of brane-bound matter this singularity can be avoided, and the negative-tension brane can shield the bulk spacetime from the singularity by bouncing back smoothly before reaching the singularity. In our analysis we compare the 5- and 4-dimensional descriptions of this phenomenon in order to determine the validity of the moduli space approximation.Comment: 20 pages, 1 figure, discussion extended and references added; minor mistake correcte

    Random RNA under tension

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    The Laessig-Wiese (LW) field theory for the freezing transition of random RNA secondary structures is generalized to the situation of an external force. We find a second-order phase transition at a critical applied force f = f_c. For f f_c, the extension L as a function of pulling force f scales as (f-f_c)^(1/gamma-1). The exponent gamma is calculated in an epsilon-expansion: At 1-loop order gamma = epsilon/2 = 1/2, equivalent to the disorder-free case. 2-loop results yielding gamma = 0.6 are briefly mentioned. Using a locking argument, we speculate that this result extends to the strong-disorder phase.Comment: 6 pages, 10 figures. v2: corrected typos, discussion on locking argument improve

    Phase-locked scroll waves defy turbulence induced by negative filament tension

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    Scroll waves in a three-dimensional media may develop into turbulence due to negative tension of the filament. Such negative tension-induced instability of scrollwaves has been observed in the Belousov-Zhabotinsky reaction systems. Here we propose a method to restabilize scroll wave turbulence caused by negative tension in three-dimensional chemical excitable media using a circularly polarized (rotating) external field. The stabilization mechanism is analyzed in terms of phase-locking caused by the external field, which makes the effective filament tension positive. The phase-locked scrollwaves that have positive tension and higher frequency defy the turbulence and finally restore order. A linear theory for the change of filament tension caused by a generic rotating external field is presented and its predictions closely agree with numerical simulations
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