119215169
Constraints on the Scalar Sector of the Renormalizable Coloron Model
The renormalizable coloron model is the minimal extension of the standard model color sector, in which the color gauge group is enlarged to SU(3)_{1c} x SU(3)_{2c}. In this paper we discuss the constraints on this model derived from the requirements of vacuum stability, tree-level unitarity, electroweak precision measurements, and from LHC measurements of the properties of the observed Higgs-like scalar boson. The combination of these theoretical and experimental considerations strongly constrains the allowed parameter space. (Erratum appended, March 2014.)
119113213
Strongly First-Order Electroweak Phase Transition and Classical Scale Invariance
In this work, we examine the possibility of realizing a strongly first-order electroweak phase transition within the minimal classically scale invariant extension of the standard model (SM), previously proposed and analyzed as a potential solution to the hierarchy problem. By introducing one complex singlet scalar and three right-handed Majorana neutrinos, the scenario was successfully capable of achieving a radiative breaking of the electroweak symmetry (Coleman-Weinberg Mechanism), inducing non-zero masses for the SM neutrinos (seesaw mechanism), presenting a pseudoscalar dark matter candidate, and predicting the existence of a second $CP$-even boson in addition to the 125 GeV scalar. We construct the full finite-temperature one-loop effective potential of the model, including the resummed thermal daisy loops, and demonstrate that finite-temperature effects induce a first-order electroweak phase transition. Requiring the thermally-driven first-order phase transition to be sufficiently strong further constrains the model's parameter space; in particular, an $\mathcal O(0.01)$ fraction of the dark matter in the universe may be simultaneously accommodated with a strongly first-order electroweak phase transition. Moreover, such a phase transition disfavors right-handed Majorana neutrino masses above several hundreds of GeV, confines the pseudoscalar dark matter masses to $\sim 1$-2 TeV, predicts the mass of the second $CP$-even scalar to be $\sim 100$-300 GeV, and requires the mixing angle between the $CP$-even components of the SM doublet and the complex singlet to lie within the range $0.2 \lesssim \sin\omega \lesssim 0.4$. The obtained results are displayed in comprehensive exclusion plots, identifying the viable regions of the parameter space. Many of these predictions lie within the reach of the next LHC run.
118713106
Technicolor in the LHC Era
LHC searches for the standard model Higgs Boson in \gamma\gamma\ or \tau\tau\ decay modes place strong constraints on the light technipion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the technipions have an enhanced production rate (largely because the technipion decay constant is smaller than the weak scale) and also enhanced branching ratios into di-photon and di-tau final states (largely due to the suppression of WW decays of the technipions). Recent ATLAS and CMS searches for Higgs bosons exclude the presence of technipions with masses from 110 GeV to nearly 2m_t in technicolor models that (a) include colored technifermions (b) feature topcolor dynamics and (c) have technicolor groups with three or more technicolors (N_{TC} > 3).
55815188
Probing Gravitational Dark Matter
So far all evidences of dark matter (DM) come from astrophysical and cosmological observations, due to gravitational interactions of the DM. It is possible that the true DM particle in the universe joins gravitational interactions only, but nothing else. Such a Gravitational DM (GDM) may act as a weakly interacting massive particle (WIMP), which is conceptually simple and attractive. In this work, we explore this direction by constructing the simplest scalar GDM particle s . It is a Z 2 odd singlet under the standard model (SM) gauge group, and naturally joins the unique dimension-4 interaction with Ricci curvature, s 2 R , where s is the dimensionless nonminimal coupling. We demonstrate that this gravitational interaction s 2 R , together with Higgs-curvature nonminimal coupling term h H y HR , induces eective couplings between 2 and SM elds, and can account for the observed DM thermal relic abundance. We analyze the annihilation cross sections of GDM particles and derive the viable parameter space for realizing the DM thermal relic density. We further study the direct/indirect detections and the collider signatures of such a scalar GDM. These turn out to be highly predictive and testable.
54201703
Higgs gravitational interaction, weak boson scattering, and Higgs inflation in Jordan and Einstein frames
We study gravitational interaction of Higgs boson through the unique dimension-4 operator xi(HHR)-H-dagger, with H the Higgs doublet and R the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling xi on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone equivalence theorem with nonzero xi coupling in both frames, and analyze the unitarity constraints. We study the xi-induced weak boson scattering cross sections at O(1 30) TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC (14 TeV) and the next generation pp colliders (50 100 TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data.
55805244
LHC constraints on a Higgs boson partner from an extended color sector
the presence of a heavy Higgs and to the detailed properties of the 125 GeV Higgs will further constrain the properties of the new heavy s scalar. Since the renormalizable coloron model may contain spectator fermions to remove anomalies, we examine several representative scenarios with different numbers of spectator fermions. Our results are summarized in plots that overlay the current exclusion limits on the s boson with the projected sensitivity of the ffiffiffi s p ¼ 14TeV LHC to the new state. We find that the upcoming LHC searches should be sensitive to an s scalar of mass less than 1 TeV for essentially all of the model parameter space in which the h state differs from the Higgs boson of the SM. More precisely, unless the mixing between the weak doublet and weak singlet gauge-eigenstate scalars is zero, the 14 TeV LHC will be sensitive to the presence of the nonstandard heavy s state that is characteristic of the renormalizable coloron model.
119415028
TACHYON FIELD-INSPIRED DARK ENERGY AND SUPERNOVAE CONSTRAINTS
The tachyon field in cosmology is studied in this paper by applying the generating function method to obtain exact solutions. The equation of state parameter of the tachyon field is , which can be expressed as a function in terms of the redshift z. Based on these solutions, we propose some tachyon-inspired dark energy models to explore the properties of the corresponding cosmological evolution. The explicit relations between the Hubble parameter and redshift enable us to test the models with SNeIa data sets easily. In this paper, we employ the SNeIa data with the parameter measured from the SDSS and the shift parameter from WMAP observations to constrain the parameters in our models.
119364316
EXACT SOLUTIONS OF EMBEDDING THE 4D UNIVERSE IN A 5D EINSTEIN MANIFOLD
One of the simplest ways to extend 4D cosmological models is to add another spatial dimension to make them 5D. In particular, it has been shown that the simplest of such 5D models, i.e. one in which the right-hand side of the Einstein equation is empty, induces a 4D nonempty universe. Accordingly, the origin of matter in a real 4D universe might be mathematically attributed to the existence of one (fictitious) extra spatial dimension. Here we consider the case of an empty 5D universe possessing a cosmological constant Λ and obtain exact solutions for both positive and negative values of the Λ. It is seen that such a model can naturally reduce to a power law ΛCDM model for the real universe. Further, it can be seen that the arbitrary constants and functions appearing in this model are endowed with definite physical meanings.
118756844
Observe the open universe in the sky
We first review the related works on the observable consequence of landscape and the regulation of e-foldings during inflation. We focus on a branch of observable consequence of landscape which predicts an open universe with negative curvature if e-foldings $N>62$. After discussing the observable regulation from the aspect by Kaloper, Kleban and Sorbo, we make an argument that in the non-flat background the observable $N$ is suppressed by a factor $k/\rho_{0}$. We point out that this seems to detect the information where e-foldings $N>62$ possibly. Finally, we discuss our outcomes with the recent work by Arkani-Hamed et al.
119744936
Neutrino Oscillation in the Space-Time with a Global Monopole
The mass neutrino interference phase in a global monopole space time along the null trajectory and the geodesic is studied, and we find that the conserved energy changes a factor when a particle travels along the geodesic, if compared with the energy in the space time without the global monopole. The oscillation phase is increased by a factor due to the correction of the global monopole, comparing with the case in Schwarzschild space time. We obtain that the type-I phase along both the null and geodesic has a difference of a factor of 1−8πη2, and that the phase along the geodesic is the double of that along the null.
119416454
Cosmology with extended Chaplygin gas media and $w=-1$ crossing
In this paper the accelerating expansion of our universe at the late cosmic evolution time in a generally modified (extended) \emph{Chaplygin gas} (Dark Fluid) model is detailed, which is characterized by two parameters ($m$, $\alpha$). Different choices to the parameters $m$ and $\alpha$ divide this model into two main kinds of situation by different properties with cosmological interests. With proper choices of parameters, we find that this extended model can realize the phantom divide $w=-1$ (Equation Of State parameter) crossing phenomenon with interesting ranges of the scale factor value $a(t)$ corresponding to $w=-1$ and present value of state parameter $w$. 
Additionally, through Taylor series expansion of the function $A(a)$ in the extended Chaplygin gas model, a specific Equation of State is gained. Under the framework of Friedman-Robertson-Walker cosmic model, it can successfully explain the accelerating expansion of our universe. However, the value of $w$ in this case is large than -1, that is, indicating it like a quintessence fluid and no $w=-1$ crossing occurs.