Notes on analytical study of holographic superconductors with Lifshitz scaling in external magnetic field

We employ the matching method to analytically investigate the holographic superconductors with Lifshitz scaling in an external magnetic field. We discuss systematically the restricted conditions for the matching method and find that this analytic method is not always powerful to explore the effect of external magnetic field on the holographic superconductors unless the matching point is chosen in an appropriate range and the dynamical exponent z satisfies the relation <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>z</mi><mo>=</mo><mi>d</mi><mo>−</mo><mn>1</mn></math> or <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>z</mi><mo>=</mo><mi>d</mi><mo>−</mo><mn>2</mn></math> . From the analytic treatment, we observe that Lifshitz scaling can hinder the condensation to be formed, which can be used to back up the numerical results. Moreover, we study the effect of Lifshitz scaling on the upper critical magnetic field and reproduce the well-known relation obtained from Ginzburg–Landau theory

Neutrino mass generation and singly charged leptonic exotics in WW events

Current measurement of leptonic WW is significantly higher than the standard model prediction which may accommodate new physics signal that mimics the leptonic decaying W . We investigate a TeV neutrino mass generation model that predicts singly charged leptonic exotics. The collider signature of this model may mimic the leptonic WW search and evade all other searches. With introduction of new SU(2)L doublet leptons, singly charged exotic leptons L± decay into L±→ℓ±ϕ where ϕ is a light singlet scalar of O(MeV) that decays into neutrinos. Drell–Yan production of L+L−→ℓ+ℓ−+E̸T fits leptonic WW searches and L±L0→ℓ±+E̸T is completely buried in SM background. In the case of direct lepton from L -decay instead of secondary decay from leptonic τ± we find the lower mass bound as 125 GeV of such exotic leptons that can be accommodated by the current measurements of WW searches at the LHC. To derive the upper bound, we employ both heavy Higgs boson search of di-lepton plus E̸T final state and leptonic W′ search of single lepton plus E̸T . Even though heavy Higgs is excluded between 260 and 640 GeV, we find LHC data can still accommodate L between 150 and 300 GeV after giving up the ηℓℓ cut. Using the single W′ search bound, we can obtain an approximate upper bound as 300 GeV

Lepton flavor violation in the Standard Model with general dimension-six operators

We study lepton flavor observables in the Standard Model (SM) extended with all dimension-6 operators which are invariant under the SM gauge group. We calculate the complete one-loop predictions to the radiative lepton decays μ → e γ, τ → μ γ and τ → e γ as well as to the closely related anomalous magnetic moments and electric dipole moments of charged leptons, taking into account all dimension-6 operators which can generate lepton flavor violation. Also the 3-body flavor violating charged lepton decays τ ± → μ ± μ + μ − , τ ± → e ± e + e − , τ ± → e ± μ + μ − , τ ± → μ ± e + e − , τ ± → e ∓ μ ± μ ± , τ ± → μ ∓ e ± e ± and μ ± → e ± e + e − and the Z 0 decays Z 0 → $\ell_i^{+}\ell_j^{-}$ are considered, taking into account all tree-level contributions

Observational constraint on the interacting dark energy models including the Sandage–Loeb test

Two types of interacting dark energy models are investigated using the type Ia supernova (SNIa), observational <math><mrow><mi>H</mi><mo stretchy="false">(</mo><mi>z</mi><mo stretchy="false">)</mo></mrow></math> data (OHD), cosmic microwave background shift parameter, and the secular Sandage–Loeb (SL) test. In the investigation, we have used two sets of parameter priors including WMAP-9 and Planck 2013. They have shown some interesting differences. We find that the inclusion of SL test can obviously provide a more stringent constraint on the parameters in both models. For the constant coupling model, the interaction term has been improved to be only a half of the original scale on corresponding errors. Comparing with only SNIa and OHD, we find that the inclusion of the SL test almost reduces the best-fit interaction to zero, which indicates that the higher-redshift observation including the SL test is necessary to track the evolution of the interaction. For the varying coupling model, data with the inclusion of the SL test show that the parameter <math><mi mathvariant="italic">ξ</mi></math> at <math><mrow><mn>1</mn><mi mathvariant="italic">σ</mi></mrow></math> C.L. in Planck priors is <math><mrow><mi mathvariant="italic">ξ</mi><mo>&gt;</mo><mn>3</mn></mrow></math> , where the constant <math><mi mathvariant="italic">ξ</mi></math> is characteristic for the severity of the coincidence problem. This indicates that the coincidence problem will be less severe. We then reconstruct the interaction <math><mrow><mi mathvariant="italic">δ</mi><mo stretchy="false">(</mo><mi>z</mi><mo stretchy="false">)</mo></mrow></math> , and we find that the best-fit interaction is also negative, similar to the constant coupling model. However, for a high redshift, the interaction generally vanishes at infinity. We also find that the phantom-like dark energy with <math><mrow><msub><mi>w</mi><mi>X</mi></msub><mo>&lt;</mo><mo>-</mo><mn>1</mn></mrow></math> is favored over the <math><mi mathvariant="italic">Λ</mi></math> CDM model

Polarization effects in early SUSY searches at the CERN LHC

An on-shell effective theory (OSET) approach has been widely used in searches of various supersymmetric signals, in particular, gluino/squark pairs with long cascade decay chains in which complete matrix element calculations may encounter high dimensional integrations. On the other hand, leptons from polarized chargino decays may show a significant boost effect in some scenarios and simulation without polarization information may underestimate or overestimate the lepton pT cut efficiencies in the first place. We study the polarization effects in leptonic decaying charginos from squarks or gluinos. Taking the polarization effects into account, we find it still justifiable to take only the OSET approach for a large parameter region, for instance, the first two generation squarks due to indistinguishable final states as well as a flat angular distribution in the motion of the lepton. On the other hand, we use the leptonic stop to illustrate the feature and find that the lepton pT cut efficiencies in cross section measurements can have maximally 25 % reduction or maximally 17 % enhancement in comparison with the kinematics-only approach. The signal rates after the cuts simulated by OSET are then underestimated/overestimated and the real bound on the squark/gluino should be more stringent or loose for a specific choice of the chargino and one can take the simulated efficiencies as a fast-simulation factor to multiply to the OSET simulated results

Non-extended phase space thermodynamics of Lovelock AdS black holes in the grand canonical ensemble

Recently, extended phase space thermodynamics of Lovelock AdS black holes has been of great interest. To provide insight from a different perspective and gain a unified phase transition picture, the non-extended phase space thermodynamics of (n+1) -dimensional charged topological Lovelock AdS black holes is investigated in detail in the grand canonical ensemble. Specifically, the specific heat at constant electric potential is calculated and the phase transition in the grand canonical ensemble is discussed. To probe the impact of the various parameters, we utilize the control variate method and solve the phase transition condition equation numerically for the cases k=1,-1 . There are two critical points for the case n=6,k=1 , while there is only one for the other cases. For k=0 , there exists no phase transition point. To figure out the nature of the phase transition in the grand canonical ensemble, we carry out an analytic check of the analog form of the Ehrenfest equations proposed by Banerjee et al. It is shown that Lovelock AdS black holes in the grand canonical ensemble undergo a second-order phase transition. To examine the phase structure in the grand canonical ensemble, we utilize the thermodynamic geometry method and calculate both the Weinhold metric and the Ruppeiner metric. It is shown that for both analytic and graphical results that the divergence structure of the Ruppeiner scalar curvature coincides with that of the specific heat. Our research provides one more example that Ruppeiner metric serves as a wonderful tool to probe the phase structures of black holes

Nonthermal two component dark matter model for Fermi-LAT γ -ray excess and 3.55 keV X-ray line

A two component model of nonthermal dark matter is formulated to simultaneously explain the Fermi-LAT results indicating a γ -ray excess observed from our Galactic Centre in the 1–3 GeV energy range and the detection of an X-ray line at 3.55 keV from extragalactic sources. Two additional Standard Model singlet scalar fields S 2 and S 3 are introduced. These fields couple among themselves and with the Standard Model Higgs doublet H . The interaction terms among the scalar fields, namely H , S 2 and S 3 , are constrained by the application of a discrete ℤ 2  × ℤ 2 ′ symmetry which breaks softly to a remnant ℤ 2 ′ ′ symmetry. This residual discrete symmetry is then spontaneously broken through an MeV order vacuum expectation value u of the singlet scalar field S 3 . The resultant physical scalar spectrum has the Standard Model like Higgs as χ 1 with M χ 1 ∼ 125 $${M}_{\chi_1}\sim 125$$ GeV, a moderately heavy scalar χ 2 with 50 GeV ≤ M χ 2 ≤ 80 $${M}_{\chi_2}\le 80$$ GeV and a light χ 3 with M χ 3 ∼ 7 $${M}_{\chi_3}\sim 7$$ keV. There is only tiny mixing between χ 1 and χ 2 as well as between χ 1 and χ 3 . The lack of importance of domain wall formation in the present scenario from the spontaneous breaking of the discrete symmetry ℤ 2 ′ ′ , provided u ≤ 10 MeV, is pointed out. We find that our proposed two component dark matter model is able to explain successfully both the above mentioned phenomena — the Fermi-LAT observed γ -ray excess (from the χ 2 → b b ¯ $${\chi}_2\to \mathrm{b}\overline{\mathrm{b}}$$ decay mode) and the observation of the X-ray line (from the decay channel χ 3 → γγ ) by the XMM-Newton observatory

Friedmann equation and the emergence of cosmic space

In this paper, we show that Padmanabhan’s conjecture for the emergence of cosmic space [arXiv:1206.4916] holds for the flat Friedmann-Robertson-Walker universe in Einstein gravity but does not hold for the non-flat case unless one uses the aerial volume instead of the proper volume. Doing this, we also show that various works extending Padmanabhan’s conjecture to non-Einstein and non-flat cases have serious shortfalls. This analysis is done using the Friedmann equation with the further assumptions of the holographic principle and the equipartition rule of energy

A density spike on astrophysical scales from an N -field waterfall transition

Hybrid inflation models are especially interesting as they lead to a spike in the density power spectrum on small scales, compared to the CMB, while also satisfying current bounds on tensor modes. Here we study hybrid inflation with N waterfall fields sharing a global SO(N) symmetry. The inclusion of many waterfall fields has the obvious advantage of avoiding topologically stable defects for N>3 . We find that it also has another advantage: it is easier to engineer models that can simultaneously (i) be compatible with constraints on the primordial spectral index, which tends to otherwise disfavor hybrid models, and (ii) produce a spike on astrophysically large length scales. The latter may have significant consequences, possibly seeding the formation of astrophysically large black holes. We calculate correlation functions of the time-delay, a measure of density perturbations, produced by the waterfall fields, as a convergent power series in both 1/N and the field's correlation function Δ(x) . We show that for large N , the two-point function is 〈δt(x)δt(0)〉∝Δ2(|x|)/N and the three-point function is 〈δt(x)δt(y)δt(0)〉∝Δ(|x−y|)Δ(|x|)Δ(|y|)/N2 . In accordance with the central limit theorem, the density perturbations on the scale of the spike are Gaussian for large N and non-Gaussian for small N

A note on Maxwell’s equal area law for black hole phase transition

The state equation of the charged AdS black hole is reviewed in the T – r+ plane. With a view on the the phase transition, the T – S , P – V , P – ν graphs are plotted and then the equal area law is used in the three cases to get the phase transition point ( P ,  T ). The analytical phase transition point relations for P – T of a charged AdS black hole has been obtained successfully. By comparing the three results, we find that the equal area law possibly cannot be used directly for the P – ν plane. According to the T – S , P – V results, we plot the P – T – Q graph and find that for a highly charged black hole a very low temperature condition is required for the phase transition