68,808 research outputs found
Fixed point scenario in the Two Higgs Doublet Model inspired by degenerate vacua
We consider the renormalisation group flow of Higgs and Yukawa couplings
within the simplest non--supersymmetric two Higgs doublet extension of the
Standard Model (SM). In this model the couplings are adjusted so that the
multiple point principle (MPP) assumption, which implies the existence of a
large set of degenerate vacua at some high energy scale , is realised.
When the top quark Yukawa coupling at the scale is large, the
solutions of RG equations in this MPP inspired 2 Higgs Doublet Model (2HDM)
converge to quasi--fixed points. We analyse the Higgs spectrum and couplings in
the quasi--fixed point scenario and compute a theoretical upper bound on the
lightest Higgs boson mass. When the scale is low, the coupling of the
SM--like Higgs scalar to the top quark can be significantly larger in the
considered model than in the SM, resulting in the enhanced production of Higgs
bosons at the LHC.Comment: 16 pages, 3 figures, CERN preprint number added, references update
Systoles of Arithmetic Hyperbolic Surfaces and 3-manifolds
Our main result is that for all sufficiently large , the set of
commensurability classes of arithmetic hyperbolic 2- or 3-orbifolds with fixed
invariant trace field and systole bounded below by has density one
within the set of all commensurability classes of arithmetic hyperbolic 2- or
3-orbifolds with invariant trace field . The proof relies upon bounds for
the absolute logarithmic Weil height of algebraic integers due to Silverman,
Brindza and Hajdu, as well as precise estimates for the number of rational
quaternion algebras not admitting embeddings of any quadratic field having
small discriminant. When the trace field is , using work of
Granville and Soundararajan, we establish a stronger result that allows our
constant lower bound to grow with the area. As an application, we
establish a systolic bound for arithmetic hyperbolic surfaces that is related
to prior work of Buser-Sarnak and Katz-Schaps-Vishne. Finally, we establish an
analogous density result for commensurability classes of arithmetic hyperbolic
3-orbifolds with small area totally geodesic -orbifolds.Comment: v4: 17 pages. Revised according to referee report. Final version. To
appear in Math. Res. Let
Design of optimized three-dimensional thrust nozzle contours
Design of optimized three-dimensional thrust nozzle contour
Fully Coherent X-ray Pulses from a Regenerative Amplifier Free Electron Laser
We propose and analyze a novel regenerative amplifier free electron laser
(FEL) to produce fully coherent x-ray pulses. The method makes use of
narrow-bandwidth Bragg crystals to form an x-ray feedback loop around a
relatively short undulator. Self-amplified spontaneous emission (SASE) from the
leading electron bunch in a bunch train is spectrally filtered by the Bragg
reflectors and is brought back to the beginning of the undulator to interact
repeatedly with subsequent bunches in the bunch train. The FEL interaction with
these short bunches not only amplifies the radiation intensity but also
broadens its spectrum, allowing for effective transmission of the x-rays
outside the crystal bandwidth. The spectral brightness of these x-ray pulses is
about two to three orders of magnitude higher than that from a single-pass SASE
FEL.Comment: 11 pages, 6 figure
A numerical study of the correspondence between paths in a causal set and geodesics in the continuum
This paper presents the results of a computational study related to the
path-geodesic correspondence in causal sets. For intervals in flat spacetimes,
and in selected curved spacetimes, we present evidence that the longest maximal
chains (the longest paths) in the corresponding causal set intervals
statistically approach the geodesic for that interval in the appropriate
continuum limit.Comment: To the celebration of the 60th birthday of Rafael D. Sorki
Double wells, scalar fields and quantum phase transitions in ions traps
Since Hund's work on the ammonia molecule, the double well potential has
formed a key paradigm in physics. Its importance is further underlined by the
central role it plays in the Landau theory of phase transitions. Recently, the
study of entanglement properties of many-body systems has added a new angle to
the study of quantum phase transitions of discrete and continuous degrees of
freedom, i.e., spin and harmonic chains. Here we show that control of the
radial degree of freedom of trapped ion chains allows for the simulation of
linear and non-linear Klein-Gordon fields on a lattice, in which the parameters
of the lattice, the non-linearity and mass can be controlled at will. The
system may be driven through a phase transition creating a double well
potential between different configurations of the ion crystal. The dynamics of
the system are controllable, local properties are measurable and tunnelling in
the double well potential would be observable.Comment: 6 pages, 5 figure
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