3,717 research outputs found

    Discriminating between technicolor and warped extra dimensional model via pp \to ZZ channel

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    We explore the possibility to discriminate between certain strongly-coupled technicolor (TC) models and warped extra-dimensional models where the Standard Model fields are propagating in the extra dimension. We consider a generic QCD-like TC model with running coupling as well as two TC models with walking dynamics. We argue that due to the different production mechanisms for the lowest-lying composite tensor state in these TC theories compared to the first Kaluza-Klein graviton mode of warped extra-dimensional case, it is possible to distinguish between these models based on the angular analysis of the reconstructed longitudinal Z bosons in the ppZZpp \to ZZ \to four charged leptons channel.Comment: 16 pages, 3 figures, 1 tabl

    Halogen bonding enhances nonlinear optical response in poled supramolecular polymers

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    We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems

    Constraints on Conformal Windows from Holographic Duals

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    We analyze a beta function with the analytic form of Novikov-Shifman-Vainshtein-Zakharov result in the five dimensional gravity-dilaton environment. We show how dilaton inherits poles and fixed points of such beta function through the zeros and points of extremum in its potential. Super Yang-Mills and supersymmetric QCD are studied in detail and Seiberg's electric-magnetic duality in the dilaton potential is explicitly demonstrated. Non-supersymmetric proposals of similar functional form are tested and new insights into the conformal window as well as determinations of scheme-independent value of the anomalous dimension at the fixed point are presented.Comment: Fig. 5b is corrected to match the discussion in the tex

    Doppler images of II Pegasi for 2004-2010

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    Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot configuration occurring on a timescale of shorter than a year. The main objective of this study is to determine whether the same phenomena persist in the star during these six years of spectroscopic monitoring. Methods. The observations were collected with the high-resolution SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results. We present 12 new temperature maps that show spots distributed mainly over high and intermediate latitudes. In each image, 1-3 main active regions can be identified. The activity level of the star is clearly lower than during our previous study for the years 1994-2002. In contrast to the previous observations, we detect no clear drift of the active regions with respect to the rotation of the star. Conclusions. Having shown a systematic longitudinal drift of the spot-generating mechanism during 1994-2002, the star has clearly switched to a low-activity state for 2004-2010, during which the spot locations appear more random over phase space. It could be that the star is near to a minimum of its activity cycle.Comment: Accepted for publication in Astron. and Astrophys., 8 pages, 5 figure

    Magnetic Doppler Imaging of Active Stars

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    We present a new implementation of the magnetic Doppler imaging technique, which aims at self-consistent temperature and magnetic mapping of the surface structures in cool active stars. Our magnetic imaging procedure is unique in its capability to model individual spectral features in all four Stokes parameters. We discuss performance and intrinsic limitations of the new magnetic Doppler imaging method. A special emphasis is given to the simultaneous modelling of the magnetically sensitive lines in the optical and infrared regions and to combining information from both atomic and molecular spectral features. These two techniques may, for the first time, give us a tool to study magnetic fields in the starspot interiors.Comment: 4 pages, 3 figures; to appear in the proceedings of Solar Polarization Workshop 5, ASP Conf. Se

    Superweakly interacting dark matter from the Minimal Walking Technicolor

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    We study a superweakly interacting dark matter particle motivated by minimal walking technicolor theories. Our WIMP is a mixture of a sterile state and a state with the charges of a standard model fourth family neutrino. We show that the model can give the right amount of dark matter over a range of the WIMP mass and mixing angle. We compute bounds on the model parameters from the current accelerator data including the oblique corrections to the precision electroweak parameters, as well as from cryogenic experiments, Super-Kamiokande and from the IceCube experiment. We show that consistent dark matter solutions exist which satisfy all current constraints. However, almost the entire parameter range of the model lies within the the combined reach of the next generation experiments.Comment: 29 pages, 6 figure

    Halogen bonding enhances nonlinear optical response in poled supramolecular polymers

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    We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems

    Critical Behavior of Non Order-Parameter Fields

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    We show that all of the relevant features of a phase transition can be determined using a non order parameter field which is a physical state of the theory. This fact allows us to understand the deconfining transition of the pure Yang-Mills theory via the physical excitations rather than using the Polyakov loop.Comment: RevTeX, 4-pages, 1 figur

    Superconductivity in Ultrasmall Metallic Grains

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    We develop a theory of superconductivity in ultrasmall (nm-scale) metallic grains having a discrete electronic eigenspectrum with a mean level spacing of order of the bulk gap. The theory is based on calculating the eigenspectrum using a generalized BCS variational approach, whose applicability has been extensively demonstrated in studies of pairing correlations in nuclear physics. We discuss how conventional mean field theory breaks down with decreasing sample size, how the so-called blocking effect weakens pairing correlations in states with non-zero total spin, and how this affects the discrete eigenspectrum's behavior in a magnetic field, which favors non-zero total spin. In ultrasmall grains, spin magnetism dominates orbital magnetism, just as in thin films in a parallel field; but whereas in the latter the magnetic-field induced transition to a normal state is known to be first-order, we show that in ultrasmall grains it is softened by finite size effects. Our calculations qualitatively reproduce the magnetic-field dependent tunneling spectra for individual aluminum grains measured recently by Ralph, Black and Tinkham. We argue that previously-discussed parity effects for the odd-even ground state energy difference are presently not observable for experimental reasons, and propose an analogous parity effect for the pair-breaking energy that should be observable provided that the grain size can be controlled sufficiently well. Finally, experimental evidence is pointed out that the dominant role played by time-reversed pairs of states, well-established in bulk and in dirty superconductors, persists also in ultrasmall grains.Comment: 21 pages RevTeX, 12 EPS figures included, uses epsf.st
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