50 research outputs found
The Planck and LHC results and particle physics
I will discuss the recent LHC and Planck results, which are completely
compatible with the Standard Model of particle physics, and the standard
cosmological model (CDM), respectively. It turns out that the
extension of the Standard Model is, of course, required, but can be very
minimal. I will discuss also what future measurements may be important to test
this approach.Comment: 7 pages, talk on the EPS-HEP 2013 prepared for conference proceeding
Why should we care about the top quark Yukawa coupling?
In the cosmological context, for the Standard Model to be valid up to the
scale of inflation, the top quark Yukawa coupling should not exceed the
critical value , coinciding with good precision (about 0.02%) with
the requirement of the stability of the electroweak vacuum. So, the exact
measurements of may give an insight on the possible existence and the
energy scale of new physics above 100 GeV, which is extremely sensitive to
. We overview the most recent theoretical computations of and
the experimental measurements of . Within the theoretical and experimental
uncertainties in the required scale of new physics varies from GeV
to the Planck scale, urging for precise determination of the top quark Yukawa
coupling.Comment: 9 pages, 8 figures. The journal version in JETP special issue. Some
discussion is improved, references added, and (here we reluctantly followed
the editorial request) the abstract is expande
Higgs inflation at the critical point
Higgs inflation can occur if the Standard Model (SM) is a self-consistent
effective field theory up to inflationary scale. This leads to a lower bound on
the Higgs boson mass, . If is more than a few
hundreds of MeV above the critical value, the Higgs inflation predicts the
universal values of inflationary indexes, and ,
independently on the Standard Model parameters. We show that in the vicinity of
the critical point the inflationary indexes acquire an
essential dependence on the mass of the top quark and . In
particular, the amplitude of the gravitational waves can exceed considerably
the universal value.Comment: Improved analysis taking into account one-loop terms in the effective
potential. Sign error in the formula for the running of the spectral index
corrected. Discussion of the relation between the particle physics and
inflationary parameters adde
Model dependence of the bremsstrahlung effects from the superluminal neutrino at OPERA
We revisit the bremsstrahlung process of a superluminal neutrino motivated by
OPERA results. From a careful analysis of the plane wave solutions of the
superluminal neutrino, we find that the squared matrix elements contain
additional terms from Lorentz violation due to the modified spin sum for the
neutrino. We point out that the coefficients of the decay rate and the energy
loss rate significantly depend on the details of the model, although the
results are parametrically similar to the ones obtained by Cohen and Glashow
[1]. We illustrate this from the modified neutral current interaction of
neutrino with Lorentz violation of the same order as in the modified dispersion
relation.Comment: 10 pages, no figures, version to appear as a Rapid Communication in
Phys. Rev.
On the robustness of the primordial power spectrum in renormalized Higgs inflation
We study the cosmological consequences of higher-dimensional operators
respecting the asymptotic symmetries of the tree-level Higgs inflation action.
The main contribution of these operators to the renormalization group enhanced
potential is localized in a compact field range, whose upper limit is close to
the end of inflation. The spectrum of primordial fluctuations in the so-called
universal regime turns out to be almost insensitive to radiative corrections
and in excellent agreement with the present cosmological data. However,
higher-dimensional operators can play an important role in critical Higgs
inflation scenarios containing a quasi-inflection point along the inflationary
trajectory. The interplay of radiative corrections with this quasi-inflection
point may translate into a sizable modification of the inflationary
observables.Comment: 12 pages, 8 figures - matches the published versio
Semiclassical S-matrix for black holes
We propose a semiclassical method to calculate S-matrix elements for
two-stage gravitational transitions involving matter collapse into a black hole
and evaporation of the latter. The method consistently incorporates
back-reaction of the collapsing and emitted quanta on the metric. We illustrate
the method in several toy models describing spherical self-gravitating shells
in asymptotically flat and AdS space-times. We find that electrically neutral
shells reflect via the above collapse-evaporation process with probability
exp(-B), where B is the Bekenstein-Hawking entropy of the intermediate black
hole. This is consistent with interpretation of exp(B) as the number of black
hole states. The same expression for the probability is obtained in the case of
charged shells if one takes into account instability of the Cauchy horizon of
the intermediate Reissner-Nordstrom black hole. Our semiclassical method opens
a new systematic approach to the gravitational S-matrix in the non-perturbative
regime.Comment: 41 pages, 13 figures; Introduction rewritten, references added;
journal versio
Standard Model Higgs boson mass from inflation
We analyse one-loop radiative corrections to the inflationary potential in
the theory, where inflation is driven by the Standard Model Higgs field. We
show that inflation is possible provided the Higgs mass m_H lies in the
interval m_min<m_H<m_max, where m_min=[136.7+(m_t-171.2)*1.95]GeV,
m_max=[184.5+(m_t-171.2)*0.5]GeV and m_t is the mass of the top quark.
Moreover, the predictions of the spectral index of scalar fluctuations and of
the tensor-to-scalar ratio practically do not depend on the Higgs mass within
the admitted region and are equal to n_s=0.97 and r=0.0034 correspondingly.Comment: 5 pages, 3 figures. Journal version+misprint fixed and added
reference to the two-loop analysis paper for convenienc
Some like it hot: heals Higgs inflation, but does not cool it
Strong coupling in Higgs inflation at high energies hinders a joint
description of inflation, reheating and low-energy dynamics. The situation may
be improved with a proper UV completion of the model. A well-defined
self-consistent way is to introduce an -term into the action. In this
modified model the strong coupling scale returns back to the Planck scale,
which justifies the use of the perturbative methods in studies of the model
dynamics after inflation. We investigate the reheating of the post-inflationary
Universe, which involves two highly anharmonic oscillators strongly interacting
with each other: homogeneous Higgs field and scalaron. We observe that in
interesting regions of model parameter space these oscillations make
longitudinal components of the weak gauge bosons tachyonic, triggering instant
preheating at timescales much shorter than the Hubble time. The weak gauge
bosons are heavy and decay promptly into light Standard Model particles,
ensuring the onset of the radiation domination era right after inflation.Comment: 18 pages, 6 figures. Minor clarifications, corrected typo in eq. (38)
and in Fig. 5 axes label