102 research outputs found
The Twin Higgs: Natural Electroweak Breaking from Mirror Symmetry
We present `twin Higgs models', simple realizations of the Higgs as a
pseudo-Goldstone boson that protect the weak scale from radiative corrections
up to scales of order 5 - 10 TeV. In the ultra-violet these theories have a
discrete symmetry which interchanges each Standard Model particle with a
corresponding particle which transforms under a twin or mirror Standard Model
gauge group. In addition, the Higgs sector respects an approximate global SU(4)
symmetry. When this global symmetry is broken, the discrete symmetry tightly
constrains the form of corrections to the pseudo-Goldstone Higgs potential,
allowing natural electroweak symmetry breaking. Precision electroweak
constraints are satisfied by construction. These models demonstrate that,
contrary to the conventional wisdom, stabilizing the weak scale does not
require new light particles charged under the Standard Model gauge groups.Comment: 5 pages. Updated to the journal versio
Embedding the Zee-Wolfenstein neutrino mass matrix in an SO(10) x A4 GUT scenario
We consider renormalizable SO(10) Yukawa interactions and put the three
fermionic 16-plets into the 3-dimensional irreducible A_4 representation.
Scanning the possible A_4 representation assignments to the scalars, we find a
unique case which allows to accommodate the down-quark and charged-lepton
masses. Assuming type II seesaw dominance, we obtain a viable scenario with the
Zee-Wolfenstein neutrino mass matrix, i.e., the Majorana mass matrix with a
vanishing diagonal. Contributions from the charged-lepton mass matrix resolve
the well-known problems with lepton mixing arising from the vanishing diagonal.
In our scenario, fermion masses and mixings are well reproduced for both normal
and inverted neutrino mass spectra, and b-tau Yukawa unification and definite
predictions for the effective mass in neutrinoless double-beta decay are
obtained.Comment: 19 pages, 3 figures, v2: final version for Phys. Rev.
Equivalence principle and experimental tests of gravitational spin effects
We study the possibility of experimental testing the manifestations of
equivalence principle in spin-gravity interactions. We reconsider the earlier
experimental data and get the first experimental bound on anomalous
gravitomagnetic moment. The spin coupling to the Earth's rotation may also be
explored at the extensions of neutron EDM and g-2 experiments. The spin
coupling to the terrestrial gravity produces a considerable effect which may be
discovered at the planned deuteron EDM experiment. The Earth's rotation should
also be taken into account in optical experiments on a search for axionlike
particles.Comment: 12 pages, version to appear in Physical Review
Generalized Parton Distributions and Description of Electromagnetic and Graviton form factors of nucleon
The new parameterization of the generalized parton distributions t-dependence
is proposed. It allows one to reproduce sufficiently well the electromagnetic
form factors of the proton and neutron at small and large momentum transfer.
The description of the data obtained by the Rosenbluth method and the
polarization method are compared. The results obtained by the latter method are
shown to be compatible with the correspondent neutron data. The impact
parameter dependence of the neutron charge density is examined. The quark
contributions to gravitational form factors of the nucleons are obtained.Comment: 9 pages, 19 figures, typos corrected, 1 fig redro
Self-consistent bounces in two dimensions
We compute bounce solutions describing false vacuum decay in a Phi**4 model
in two dimensions in the Hartree approximation, thus going beyond the usual
one-loop corrections to the decay rate. We use zero energy mode functions of
the fluctuation operator for the numerical computation of the functional
determinant and the Green's function. We thus avoid the necessity of
discretizing the spectrum, as it is necessary when one uses numerical
techniques based on eigenfunctions. Regularization is performed in analogy of
standard perturbation theory; the renormalization of the Hartree approximation
is based on the two-particle point-irreducible (2PPI) scheme. The iteration
towards the self-consistent solution is found to converge for some range of the
parameters. Within this range we find the corrections to the leading one-loop
approximation to be relatively small, not exceeding one order of magnitude in
the total transition rate.Comment: 30 pages, 12 figure
Hyperfine Level Splitting for Hydrogen-Like Ions due to Rotation-Spin Coupling
The theoretical aspects of spin-rotation coupling are presented. The approach
is based on the general covariance principle. It is shown that the
gyrogravitational ratio of the bare spin-1/2 and the spin-1 particles is equal
unity. That is why spin couples with rotation as an ordinary angular momentum.
This result is the rigorous substantiation of the cranking model. To observe
the phenomenon, the experiment with hydrogen-like ions in a storage ring is
suggested. It is found that the splitting of the
hyperfine state of the and ions
circulating in the storage ring ESR in Darmstadt along a helical trajectory is
about 4.5 MHz. We argue that such splitting can be experimentally determined by
means of the ionic interferometry.Comment: 6 pages, final versio
Relativistic quantum model of confinement and the current quark masses
We consider a relativistic quantum model of confined massive spinning quarks
and antiquarks which describes leading Regge trajectories of mesons. The quarks
are described by the Dirac equations and the gluon contribution is approximated
by the Nambu-Goto straight-line string. The string tension and the current
quark masses are the main parameters of the model. Additional parameters are
phenomenological constants which approximate nonstring short-range
contributions. Comparison of the measured meson masses with the model
predictions allows one to determine the current quark masses (in MeV) to be
. The chiral
model[23] makes it possible to estimate from here the - and -quark masses
to be ~ Mev and Mev.Comment: 15 pages, LATEX, 2 tables. (submitted to Phys.Rev.D
Neutron - Mirror Neutron Oscillations: How Fast Might They Be?
We discuss the phenomenological implications of the neutron (n) oscillation
into the mirror neutron (n'), a hypothetical particle exactly degenerate in
mass with the neutron but sterile to normal matter. We show that the present
experimental data allow a maximal n-n' oscillation in vacuum with a
characteristic time much shorter than the neutron lifetime, in fact as
small as 1 sec. This phenomenon may manifest in neutron disappearance and
regeneration experiments perfectly accessible to present experimental
capabilities and may also have interesting astrophysical consequences, in
particular for the propagation of ultra high energy cosmic rays.Comment: 4 pages, 1 figure; revtex; matches paper published by P.R.
Statistics of resonance poles, phase shifts and time delays in quantum chaotic scattering for systems with broken time reversal invariance
Assuming the validity of random matrices for describing the statistics of a
closed chaotic quantum system, we study analytically some statistical
properties of the S-matrix characterizing scattering in its open counterpart.
In the first part of the paper we attempt to expose systematically ideas
underlying the so-called stochastic (Heidelberg) approach to chaotic quantum
scattering. Then we concentrate on systems with broken time-reversal invariance
coupled to continua via M open channels. By using the supersymmetry method we
derive:
(i) an explicit expression for the density of S-matrix poles (resonances) in
the complex energy plane
(ii) an explicit expression for the parametric correlation function of
densities of eigenphases of the S-matrix.
We use it to find the distribution of derivatives of these eigenphases with
respect to the energy ("partial delay times" ) as well as with respect to an
arbitrary external parameter.Comment: 51 pages, RevTEX , three figures are available on request. To be
published in the special issue of the Journal of Mathematical Physic
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