20,798 research outputs found

### Gauge glass in two dimensions

The gauge glass model offers an interesting example of a randomly frustrated
system with a continuous O(2) symmetry. In two dimensions, the existence of a
glass phase at low temperatures has long been disputed among numerical studies.
To resolve this controversy, we examine the behavior of vortices whose movement
generates phase slips that destroy phase rigidity at large distances. Detailed
analytical and numerical studies of the corresponding Coulomb gas problem in a
random potential establish that the ground state, with a finite density of
vortices, is polarizable with a scale-dependent dielectric susceptibility.
Screening by vortex/antivortex pairs of arbitrarily large size is present to
eliminate the logarithmic divergence of the Coulomb energy of a single vortex.
The observed power-law decay of the Coulomb interaction between vortices with
distance in the ground state leads to a power-law divergence of the glass
correlation length with temperature $T$. It is argued that free vortices
possess a bound excitation energy and a nonzero diffusion constant at any
$T>0$.Comment: 10 pages, no figure, to appear in Proceedings of YKIS 2009 Workshop:
Frontiers of Nonequilibrium Physic

### Study of the heavy CP-even Higgs with mass 125 GeV in two-Higgs-doublet models at the LHC and ILC

We assume that the 125 GeV Higgs discovered at the LHC is the heavy CP-even
Higgs of the two-Higgs-doublet models, and examine the parameter space in the
Type-I, Type-II, Lepton-specific and Flipped models allowed by the latest Higgs
signal data, the relevant experimental and theoretical constraints. Further, we
show the projected limits on $\tan\beta$, $\sin(\beta-\alpha)$, $Hf\bar{f}$ and
$HVV$ couplings from the future measurements of the 125 GeV Higgs at the LHC
and ILC, including the LHC with integrated luminosity of 300 fb$^{-1}$ (LHC-300
fb$^{-1}$) and 3000 fb$^{-1}$ (LHC-3000 fb$^{-1}$) as well as the ILC at
$\sqrt{s}=250$ GeV (ILC-250 GeV), $\sqrt{s}=500$ GeV (ILC-500 GeV) and
$\sqrt{s}=1000$ GeV (ILC-1000 GeV). Assuming that the future Higgs signal data
have no deviation from the SM expectation, the LHC-300 fb$^{-1}$, LHC-3000
fb$^{-1}$ and ILC-1000 GeV can exclude the wrong-sign Yukawa coupling regions
of the Type-II, Flipped and Lepton-specific models at the $2\sigma$ level,
respectively. The future experiments at the LHC and ILC will constrain the
Higgs couplings to be very close to SM values, especially for the $HVV$
coupling.Comment: 22 pages, 3 tables, 6 figures. Version accepted for publication in
JHE

### Rare-event induced binding transition of heteropolymers

Sequence heterogeneity broadens the binding transition of a polymer onto a
linear or planar substrate. This effect is analyzed in a real-space
renormalization group scheme designed to capture the statistics of rare events.
In the strongly disordered regime, binding initiates at an exponentially rare
set of ``good contacts''. Renormalization of the contact potential yields a
Kosterlitz-Thouless type transition in any dimension. This and other
predictions are confirmed by extensive numerical simulations of a directed
polymer interacting with a columnar defect.Comment: 4 pages, 3 figure

### A simplified 2HDM with a scalar dark matter and the galactic center gamma-ray excess

Due to the strong constrain from the LUX experiment, the scalar portal dark
matter can not generally explain a gamma-ray excess in the galactic center by
the annihilation of dark matter into $b\bar{b}$. With the motivation of
eliminating the tension, we add a scalar dark matter to the aligned
two-Higgs-doublet model, and focus on a simplified scenario, which has two main
characteristics: (i) The heavy CP-even Higgs is the discovered 125 GeV Higgs
boson, which has the same couplings to the gauge bosons and fermions as the SM
Higgs. (ii) Only the light CP-even Higgs mediates the dark matter interactions
with SM particles, which has no couplings to $WW$ and $ZZ$, but the independent
couplings to the up-type quarks, down-type quarks and charged leptons. We find
that the tension between $_{SS\to b\bar{b}}$ and the constraint from
LUX induced by the scalar portal dark matter can go away for the
isospin-violating dark matter-nucleon coupling with $-1.0< f^n/f^p<0.7$, and
the constraints from the Higgs search experiments and the relic density of
Planck are also satisfied.Comment: 12 pages, 3 figures, 1 table; reference adde

### Status of the aligned two-Higgs-doublet model confronted with the Higgs data

Imposing the theoretical constraints from vacuum stability, unitarity and
perturbativity as well as the experimental constraints from the electroweak
precision data, flavor observables and the non-observation of additional Higgs
at collider, we study the implications of available Higgs signals on a
two-Higgs-doublet model with the alignment of the down-type quarks and charged
lepton Yukawa coupling matrices. Compared to the four traditional types of
two-Higgs-doublet models, the model has two additional mixing angles $\theta_d$
and $\theta_l$ in the down-type quark and charged lepton Yukawa interactions.
We find that the mixing angle $\theta_d$ can loose the constraints on
$sin(\beta-\alpha)$, $tan\beta$ and $m_{H^{\pm}}$ sizably. The model can
provide the marginally better fit to available Higgs signals data than SM,
which requires the Higgs couplings with gauge bosons, $u\bar{u}$ and $d\bar{d}$
to be properly suppressed, and favors (1 <\theta_d< 2, 0.5 <\theta_l< 2.2) for
$m_h=$ 125.5 GeV and (0.5 <\theta_d< 2, 0.5 <\theta_l< 2.2) for $m_H=$ 125.5
GeV. However, these Higgs couplings are allowed to have sizable deviations from
SM for ($m_h=$ 125.5 GeV, 125.5 $\leq m_H\leq$ 128 GeV) and (125 GeV $\leq
m_h\leq$ 125.5 GeV, $m_H=$ 125.5 GeV).Comment: 21 pages, 9 figures and 3 tables. Final version appeared in JHE

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