117009475
Quantum effect on luminosity-redshift relation
There are many different proposals for a theory of quantum gravity. Even leaving aside the fundamental difference among theories such as the string theory and the non-perturbative quantum gravity, we are still left with many ambiguities (and/or parameters to be determined) with regard to the choice of variables, the choice of related groups, etc. Loop quantum gravity is also in such a state. It is interesting to search for experimental observables to distinguish these quantum schemes. This paper investigates the loop quantum gravity effect on luminosity-redshift relation. The quantum bounce behavior of loop quantum cosmology is found to result in multivalued correspondence in luminosity-redshift relation. And the detail multivalued behavior can tell the difference of different quantum parameters. The inverse volume quantum correction does not result in bounce behavior in this model, but affects luminosity-redshift relation also significantly.
119308824
Phenomenology analysis of duration inflation for tachyon field in loop quantum cosmology
Assuming that the e-folding number is just determined by the change of the scale factor, the tachyonic inflation theory in loop quantum cosmology (LQC) has been discussed. Considering the tachyon field with exponential potential and inverse quadratic potential, we find that the evolutionary pictures of super inflation are affected by the potentials and the initial conditions. However it cannot provide enough e-folding number, no matter which condition is chosen. Therefore a slow-rolling inflation is necessary. The e-folding number for slow-rolling inflation depends on the values of the parameter α of the exponential potential and the initial conditions. To get enough e-folding number, α should be small. Based on the slow-rolling inflation happens immediately when the super inflation ends, and the scale factor continuously grows during the whole inflation stage, we consider an e-folding number provided by the whole inflationary stage, and we find that it is easier to get enough e-folding number when the sc...
119220991
Warm inflation in loop quantum cosmology: a model with a general dissipative coefficient
A general form of warm inflation with the dissipative coefficient $\ensuremath{\Gamma}={\ensuremath{\Gamma}}_{0}(\ensuremath{\phi}/{\ensuremath{\phi}}_{0}{)}^{n}(T/{\ensuremath{\tau}}_{0}{)}^{m}$ in loop quantum cosmology is studied. In this case, we obtain conditions for the existence of a warm inflationary attractor in the context of loop quantum cosmology by using the method of stability analysis. The two cases when the dissipative coefficient is independent ($m=0$) and dependent ($m\ensuremath{\ne}0$) on temperature are analyzed specifically. In the latter case, we use the new power spectrum which should be used when considering temperature dependence in the dissipative coefficient. We find that the thermal effect is enhanced in the case $mg0$. As in the standard inflation in loop quantum cosmology, we also reach the conclusion that quantum effect leaves a tiny imprint on the cosmic microwave background sky.
119090641
VIOLATION OF STRONG ENERGY CONDITION IN EFFECTIVE LOOP QUANTUM COSMOLOGY
In loop quantum cosmology nonperturbative modification to a scalar matter field at short scales implies inflation which also means a violation of the strong energy condition. In the framework of effective Hamiltonian we discuss the issue of violation of the strong energy condition in the presence of quantum geometry potential. It is shown that the appearance of quantum geometry potential strengthens the violation of the strong energy condition in small volume regions. In the small volume regions superinflation can easily happen. Furthermore, when the evolution of the universe approaches the bounce scale, this trend of violating the strong energy condition can be greatly amplified.
122770000
Quantum thermal effect of arbitrarily accelerating Kinnersley black hole
The Hawking radiation of an arbitrarily accelerating Kinnersley black hole is studied. We obtain the event horizon equation and the Hawking thermal spectrum formula. Both the location and the temperature of the event horizon depend on the time and the angles. We recover the well-known results when the acceleration vanishes.
118389942
DYNAMICAL BEHAVIOR OF INTERACTING DARK ENERGY IN LOOP QUANTUM COSMOLOGY
The dynamical behaviors of interacting dark energy in loop quantum cosmology are discussed in this paper. Based on three defined dimensionless variables, we simplify the equations of the fixed points. The fixed points for interacting dark energy can be determined by the Friedmann equation coupled with the dynamical equations in Einstein cosmology. But in loop quantum cosmology, besides the Friedmann equation, the conversation equation also gives a constrain on the fixed points. The difference of stability properties for the fixed points in loop quantum cosmology and the ones in Einstein cosmology are also discussed.
118505781
A SM-like Higgs near 125 GeV in low energy SUSY: a comparative study for MSSM and NMSSM
A bstractMotivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling At) and calculate the rates of the di-photon signal and the V V* (V = W, Z) signals at the LHC. Our typical findings are: (i) In the MSSM the top squark and At must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ii) In the MSSM a light stau is needed to enhance the di- photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (iii) In the MSSM the signal rates of pp → h → V V* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (iv) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).
119294466
Little Higgs theory confronted with the LHC Higgs data
We confront the little Higgs theory with the LHC Higgs search data (up to 17 fb(-1) of the combined 7 and 8 TeV run). Considering some typical models, namely, the littlest Higgs model, the littlest Higgs model with T parity (LHT-A and LHT-B), and the simplest little Higgs model, we scan over the parameter space in the region allowed by current experiments. We find that in these models the inclusive and exclusive (via gluon-gluon fusion) diphoton and ZZ* signal rates of the Higgs boson are always suppressed and approach the standard model predictions for a large-scale f. Thus, the ZZ* signal rate is within the 1 sigma range of the experimental data while the inclusive diphoton signal rate is always outside the 2 sigma range. Especially, in the LHT-A the diphoton signal rate is outside the 3 sigma range of the experimental data for f < 800 GeV. We also perform a global chi(2) fit to the available LHC and Tevatron Higgs data, and find that these models provide no better global fit to the whole data set (only for some special channels a better fit can be obtained, especially in the LHT-B). DOI: 10.1103/PhysRevD.87.055004
119235151
Higgs decay to dark matter in low energy SUSY: is it detectable at the LHC?
A bstractDue to the limited statistics so far accumulated in the Higgs boson search at the LHC, the Higgs boson property has not yet been tightly constrained and it is still allowed for the Higgs boson to decay invisibly to dark matter with a sizable branching ratio. In this work, we perform a comparative study for the Higgs decay to neutralino dark matter by considering three different low energy SUSY models: the minimal supersymmetric standard model (MSSM), the next-to-minimal supersymmetric standard models (NMSSM) and the nearly minimal supersymmetric standard model (nMSSM). Under current experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density), we scan over the parameter space of each model. Then in the allowed parameter space we calculate the branching ratio of the SM-like Higgs decay to neutralino dark matter and examine its observability at the LHC by considering three production channels: the weak boson fusion VV → h, the associated production with a Z-boson pp → hZ + X or a pair of top quarks $pp \to ht\overline t + X$. We find that in the MSSM such a decay is far below the detectable level; while in both the NMSSM and nMSSM the decay branching ratio can be large enough to be observable at the LHC. We conclude that at the LHC the interplay of detecting such an invisible decay and the visible di-photon decay may allow for a discrimination of different SUSY models.
16593749
Recent Electroweak Results from the Tevatron
W and Z bosons are mainly produced via quark-antiquark annihilations at the Fermilab Tevatron collider. Precision measurements with these gauge bosons provide us with high precision tests of the Standard Model (SM) as well as indirect search for possible new physics beyond the SM. I present the recent electroweak measurements related to single W, Z boson and diboson productions from the CDF and D0 experiments at the Fermilab Tevatron collider.
109816638
The RPC-based proposal for the ATLAS forward muon trigger upgrade in view of super-LHC
The innermost station of the present ATLAS forward muon detector needs to be upgraded for the super-LHC. We present a proposal to replace it with a sandwiched detector composed of several layers of small-radius Monitored Drift Tube chambers (sMDT) for precision tracking measurement and two stations of multi-gap Resistive Plate Chambers (mRPC) for triggering purpose. We describe the layout of the upgraded detector and the trigger strategy. Several modifications to the RPCs used in the ATLAS barrel region are needed to satisfy the super-LHC requirements. Various studies with the proposed mRPC timing resolution, spatial resolution and rate capability have been performed.