3,421 research outputs found

    Mooses, Topology and Higgs

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    New theories of electroweak symmetry breaking have recently been constructed that stabilize the weak scale and do not rely upon supersymmetry. In these theories the Higgs boson is a weakly coupled pseudo-Goldstone boson. In this note we study the class of theories that can be described by theory spaces and show that the fundamental group of theory space describes all the relevant classical physics in the low energy theory. The relationship between the low energy physics and the topological properties of theory space allow a systematic method for constructing theory spaces that give any desired low energy particle content and potential. This provides us with tools for analyzing and constructing new theories of electroweak symmetry breaking.Comment: 16 pages, 11 figure

    Higher dimensional supersymmetry in 4D superspace

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    We present an explicit formulation of supersymmetric Yang-Mills theories from \D= 5 to 10 dimensions in the familiar \N=1,\D=4 superspace. This provides the rules for globally supersymmetric model building with extra dimensions and in particular allows us to simply write down N=1\N=1 SUSY preserving interactions between bulk fields and fields localized on branes. We present a few applications of the formalism by way of illustration, including supersymmetric ``shining'' of bulk fields, orbifolds and localization of chiral fermions, anomaly inflow and super-Chern-Simons theories.Comment: Typos corrected. Added reference to early work by Marcus, Sagnotti and Siegel and a term to the non-Abelian Lagrangian for D>5 formally needed for gauge invariance. The results however remain unchange

    Infinitely Large New Dimensions

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    We construct intersecting brane configurations in Anti-de-Sitter space localizing gravity to the intersection region, with any number nn of extra dimensions. This allows us to construct two kinds of theories with infinitely large new dimensions, TeV scale quantum gravity and sub-millimeter deviations from Newton's Law. The effective 4D Planck scale MPlM_{Pl} is determined in terms of the fundamental Planck scale MM_* and the AdSAdS radius of curvature LL via the familiar relation MPl2M2+nLnM_{Pl}^2 \sim M_{*}^{2+n} L^n; LL acts as an effective radius of compactification for gravity on the intersection. Taking MM_* \sim TeV and LL \sim sub-mm reproduces the phenomenology of theories with large extra dimensions. Alternately, taking ML1MPlM_* \sim L^{-1} \sim M_{Pl}, and placing our 3-brane a distance 100MPl1\sim 100 M_{Pl}^{-1} away from the intersection gives us a theory with an exponential determination of the Weak/Planck hierarchy.Comment: 4 pages, revtex, no figure

    Phenomenology of Electroweak Symmetry Breaking from Theory Space

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    Recently, a new class of realistic models for electroweak symmetry breaking have been constructed, without supersymmetry. These theories have naturally light Higgs bosons and perturbative new physics at the TeV scale. We describe these models in detail, and show that electroweak symmetry breaking can be triggered by a large top quark Yukawa coupling. A rich spectrum of particles is predicted, with a pair of light Higgs doublets accompanied by new light weak triplet and singlet scalars. The lightest of these new scalars is charged under a geometric discrete symmetry and is therefore stable, providing a new candidate for WIMP dark matter. At TeV energies, a plethora of new heavy scalars, gauge bosons and fermions are revealed, with distinctive quantum numbers and decay modes.Comment: 22 pages, latex, 6 figures. Numerical results corrected, clarifications added, conclusions unchange

    The Momentum Amplituhedron

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    In this paper we define a new object, the momentum amplituhedron, which is the long sought-after positive geometry for tree-level scattering amplitudes in N = 4 super Yang-Mills theory in spinor helicity space. Inspired by the construction of the ordinary amplituhedron, we introduce bosonized spinor helicity variables to represent our external kinematical data, and restrict them to a particular positive region. The momentum amplituhedron M n,k is then the image of the positive Grassmannian via a map determined by such kinematics. The scattering amplitudes are extracted from the canonical form with logarithmic singularities on the boundaries of this geometry.Peer reviewedFinal Published versio

    Decoupling Solution to SUSY Flavor Problem via Extra Dimensions

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    We discuss the decoupling solution to SUSY flavor problem in the fat brane scenario. We present a simple model to yield the decoupling sfermion spectrum in a five dimensional theory. Sfermion masses are generated by the overlap between the wave functions of the matter fields and the chiral superfields on the SUSY breaking brane. Two explicit examples of the spectrum are given.Comment: 8 pages, LaTe

    Causality, Analyticity and an IR Obstruction to UV Completion

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    We argue that certain apparently consistent low-energy effective field theories described by local, Lorentz-invariant Lagrangians, secretly exhibit macroscopic non-locality and cannot be embedded in any UV theory whose S-matrix satisfies canonical analyticity constraints. The obstruction involves the signs of a set of leading irrelevant operators, which must be strictly positive to ensure UV analyticity. An IR manifestation of this restriction is that the "wrong" signs lead to superluminal fluctuations around non-trivial backgrounds, making it impossible to define local, causal evolution, and implying a surprising IR breakdown of the effective theory. Such effective theories can not arise in quantum field theories or weakly coupled string theories, whose S-matrices satisfy the usual analyticity properties. This conclusion applies to the DGP brane-world model modifying gravity in the IR, giving a simple explanation for the difficulty of embedding this model into controlled stringy backgrounds, and to models of electroweak symmetry breaking that predict negative anomalous quartic couplings for the W and Z. Conversely, any experimental support for the DGP model, or measured negative signs for anomalous quartic gauge boson couplings at future accelerators, would constitute direct evidence for the existence of superluminality and macroscopic non-locality unlike anything previously seen in physics, and almost incidentally falsify both local quantum field theory and perturbative string theory.Comment: 34 pages, 10 figures; v2: analyticity arguments improved, discussion on non-commutative theories and minor clarifications adde

    Experimental results on searches beyond the Standard Model

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    Recent results for direct searches for physics beyond the Standard Model are reviewed. The results include Tevatron II data up to 1.2 fb-1 and HERA results up to 350 pb-1. Searches for Supersymmetry, for compositeness and for large extra dimensions are presented. The excess of events with an isolated lepton and high missing transverse momentum at HERA is discussed.Comment: 10 pages, 15 figures, Plenary talk at the ICHEP06 conference, Moscow, July 26-August 2, 200

    Experimental hints of Gravity in Large Extra Dimensions?

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    Recent conjectures suggest the universe may have large extra dimensions, through which gravity propagates. This implies gross departures from Newton's law of gravity at small length scales. Here I consider some implications for particle dynamics on scales comparable to the compactification radius, R_c \ltorder 1 mm. During planet formation, coalescence of micron sized dust grains to planetesimals is a rate critical step. Blum et al (2000) found dust grain aggregates form low fractal dimension structures in microgravity, consistent with high angular momentum coalescence. I consider the effects of non-Newtonian gravity on dust aggregation on scales less than RcR_c and show they naturally coalesce into low dimensional structures with high specific angular momentum. We infer Rc80R_c \approx 80 microns.Comment: 5 pages, revtex, Int. Jour. Mod. Phys. D (Special issue of GRF essays 2001), single spaced versio

    Testing gravity in Large Extra Dimensions using Bose-Einstein Condensates

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    Recent conjectures that there are mesoscopically ``large'' extra dimensions, through which gravity propagates have interesting implications for much of physics. The scenario implies gross departures from Newton's law of gravity at small length scales. Testing departures from Coulomb's law on sub-millimetre scales is hard. It is now possible to routinely create Bose-Einstein condensates with de Broglie wavelengths of order a μm\mu m and total size of order 10μm10 \mu m. BEC condensates move coherently under gravitational acceleration, and I propose that the transverse fringe shift due to the acceleration of pair of interfering BECs passing a dense linear mass may be measurable, and provide direct evidence for anomalous gravitational acceleration. Ideally such experiments are best carried out in free fall to maximise the time spent by a BEC in the non-Newtonian regime.Comment: 2 pages, double column, revtex, no figures Int J. Mod Phys D. (Special issue of GRF essays 2002). Int. J. Mod. Phys. D. in pres
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