233 research outputs found

    Collider Production of TeV Scale Black Holes and Higher-Curvature Gravity

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    We examine how the production of TeV scale black holes at colliders is influenced by the presence of Lovelock higher-curvature terms in the action of models with large extra dimensions. Such terms are expected to arise on rather general grounds, e.g., from string theory and are often used in the literature to model modifications to the Einstein-Hilbert action arising from quantum and/or stringy corrections. While adding the invariant which is quadratic in the curvature leads to quantitative modifications in black hole properties, cubic and higher invariants are found to produce significant qualitative changes, e.g., classically stable black holes. We use these higher-order curvature terms to construct a toy model of the black hole production cross section threshold. For reasonable parameter values we demonstrate that detailed measurements of the properties of black holes at future colliders will be highly sensitive to the presence of the Lovelock higher-order curvature terms.Comment: 37 pages, 11 figures, references adde

    A covariant approach to general field space metric in multi-field inflation

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    We present a covariant formalism for general multi-field system which enables us to obtain higher order action of cosmological perturbations easily and systematically. The effects of the field space geometry, described by the Riemann curvature tensor of the field space, are naturally incorporated. We explicitly calculate up to the cubic order action which is necessary to estimate non-Gaussianity and present those geometric terms which have not yet known before.Comment: (v1) 18 pages, 1 figure; (v2) references added, typos corrected, to appear in Journal of Cosmology and Astroparticle Physics; (v3) typos in (54), (62) and (64) correcte

    An integral equation approach to effective interactions between polymers in solution

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    We use the thread model for linear chains of interacting monomers, and the ``polymer reference interaction site model'' (PRISM) formalism to determine the monomer-monomer pair correlation function hmm(r)h_{mm}(r) for dilute and semi-dilute polymer solutions, over a range of temperatures from very high (where the chains behave as self-avoiding walks) to below the θ\theta temperature, where phase separation sets in. An inversion procedure, based on the HNC integral equation, is used to extract the effective pair potential between ``average'' monomers on different chains. An accurate relation between hmm(r)h_{mm}(r), hcc(r)h_{cc}(r) [the pair correlation function between the polymer centers of mass (c.m.)], and the intramolecular form factors is then used to determine hcc(r)h_{cc}(r), and subsequently extract the effective c.m.-c.m. pair potential vcc(r)v_{cc}(r) by a similar inversion procedure. vcc(r)v_{cc}(r) depends on temperature and polymer concentration, and the predicted variations are in reasonable agreement with recent simulation data, except at very high temperatures, and below the θ\theta temperature.Comment: 13 pages, 13 figures, revtex ; revised versio

    Present and Future CP Measurements

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    We review theoretical and experimental results on CP violation summarizing the discussions in the working group on CP violation at the UK phenomenology workshop 2000 in Durham.Comment: 104 pages, Latex, to appear in Journal of Physics

    Localized Character of 4f Electrons in CeRhx_x(x=2,3) and CeNix_x(x=2,5)

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    We have measured Ce 4f spectral weights of extremely α\alpha-like Ce-transition metal intermetallic compounds CeRhx_x (x=2,3) and CeNix_x (x=2,5) by using the {\it bulk-sensitive} resonant photoemission technique at the Ce M5M_5(3d5/24f3d_{5/2}\to4f)-edge. Unprecedentedly high energy resolution and longer escape depth of photoemitted electron at this photon energy enabled us to distinguish the sharp Kondo resonance tails at the Fermi level, which can be well described by the Gunnarsson-Sch\"onhammer(GS) calculation based on the Anderson Impurity Hamiltonian. On the other hand, the itinerant 4f band description shows big discrepancies, which implies that Ce 4f electrons retain localized characters even in extremely α\alpha-like compounds.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

    Effective Field Theories and Inflation

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    We investigate the possible influence of very-high-energy physics on inflationary predictions focussing on whether effective field theories can allow effects which are parametrically larger than order H^2/M^2, where M is the scale of heavy physics and H is the Hubble scale at horizon exit. By investigating supersymmetric hybrid inflation models, we show that decoupling does not preclude heavy-physics having effects for the CMB with observable size even if H^2/M^2 << O(1%), although their presence can only be inferred from observations given some a priori assumptions about the inflationary mechanism. Our analysis differs from the results of hep-th/0210233, in which other kinds of heavy-physics effects were found which could alter inflationary predictions for CMB fluctuations, inasmuch as the heavy-physics can be integrated out here to produce an effective field theory description of low-energy physics. We argue, as in hep-th/0210233, that the potential presence of heavy-physics effects in the CMB does not alter the predictions of inflation for generic models, but does make the search for deviations from standard predictions worthwhile.Comment: 19 pages, LaTeX, no figures, uses JHEP

    Surgical treatment of zygomatic bone fracture using two points fixation versus three point fixation-a randomised prospective clinical trial

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    <p>Abstract</p> <p>Background</p> <p>The zygoma plays an important role in the facial contour for both cosmetic and functional reasons; therefore zygomatic bone injuries should be properly diagnosed and adequately treated. Comparison of various surgical approaches and their complications can only be done objectively using outcome measurements which in turn require protocol management and long-term follow up. The preference for open reduction and internal fixation of zygomatic fractures at three points has continued to grow in response to observations of inadequate results from two point and one point fixation techniques.</p> <p>The objectives of this study were to compare the efficacy of zygomatic bone after treatment with ORIF using 2 point fixation and ORIF using 3 point fixation and compare the outcome of two procedures.</p> <p>Methods</p> <p>100 patients were randomly divided equally into two groups. In group A, 50 patients were treated by ORIF using two point fixation by miniplates and in group B, 50 patients were treated by ORIF using three point fixation by miniplates. They were evaluated for their complications during and after surgery with their advantages and disadvantages and the difference between the two groups was observed.</p> <p>Results</p> <p>A total of 100 fractures were sustained. We found that postoperative complication like decreased malar height and vertical dystopia was more common in those patients who were treated by two point fixation than those who were treated with three point fixation.</p> <p>Conclusions</p> <p>Based on this study open reduction and internal fixation using three point fixation by miniplates is the best available method for the treatment zygomatic bone fractures.</p

    Role of Portal Vein Embolization in Hepatocellular Carcinoma Management and Its Effect on Recurrence: A Case-control Study

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    Background Liver regeneration that occurs after portal vein embolization (PVE) may have adverse effects on the microscopic tumor foci in the residual liver mass in patients with hepatocellular carcinoma (HCC). Methods Fifty-four HCC patients with inadequate functional residual liver volume were offered PVE during a seven-year period. Among them, 34 (63%) patients underwent curative resection. They were compared with a matched control group (n = 102) who underwent surgery without PVE. Postoperative complications, pattern of recurrence, and survival were compared between groups. Results In the PVE group, a pre-embolization functional residual liver volume of 23% (12-33.5%) improved to 34% (20-54%) (p = 0.005) at the time of surgery. When the two groups were compared, minor (PVE, 24%; control, 29%; p = 0.651) and major (PVE, 18%; control, 15%; p = 0.784) complications were similar. After a follow-up period of 35 months (standard deviation 25 months), extrahepatic recurrences were detected in 10 PVE patients (29%) and 41 control patients (40%) (p = 0.310). Intrahepatic recurrences were seen in 10 (29%) and 47 (46%) cases (p = 0.109) in the PVE and control groups, respectively. In the PVE group, 41% (n = 14) of the recurrences were detected before one year, compared with 42% (n = 43) in the control group (p = 1). Disease-free survival rates at 1, 3, and 5 years were 57, 29, and 26% in the control group and 60, 42, and 42% in the PVE group (log-rank, p = 0.335). On multivariate analysis, PVE was not a factor affecting survival (p = 0.821). Conclusions Portal vein embolization increases the resectability of initially unresectable HCC due to inadequate functional residual liver volume, and it has no deleterious oncological effect after major resection of HCC. © The Author(s) 2012.published_or_final_versionSpringer Open Choice, 28 May 201
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