We investigate quasinormal modes of a massless charged scalar field on a small Reissner-Nordström-anti-de Sitter (RN-AdS) black hole both with analytical and numerical approaches. In the analytical approach, by using the small black hole approximation ($r_{+}\ll L$), we obtain the quasinormal mode frequencies in the limit of $r_{+}/L\to 0$, where $r_{+}$ and $L$ stand for the black hole event horizon radius and the AdS scale, respectively. We then show that the small RN-AdS black hole is unstable if its quasinormal modes satisfy the superradiance condition and that the instability condition of the RN-AdS black hole in the limit of $r_{+}/L\to 0$ is given by $Q>\frac{3}{eL}{Q}_c$, where $Q$, $Q_c$, and $e$ are the charge of the black hole, the critical (maximum) charge of the black hole, and the charge of the scalar field, respectively. In the numerical approach, we calculate the quasinormal modes for the small RN-AdS black holes with $r_{+}\ll L$ and confirm that the RN-AdS black hole is unstable if its quasinormal modes satisfy the superradiance condition. Our numerical results show that the RN-AdS black holes with $r_{+}=0.2L$, $0.1L$, and $0.01L$ become unstable against scalar perturbations with $eL=4$ when the charge of the black hole satisfies $Q\gtrsim 0.8Q_c$, $0.78Q_c$, and $0.76Q_c$, respectively.

We carefully investigate the modified Einstein’s field equation in a 4-dimensional (3-brane) arbitrary manifold embedded in a 5-dimensional non-Riemannian bulk spacetime with a noncompact extra dimension. In this context the Israel-Darmois matching conditions are extended assuming that the torsion in the bulk is continuous. The discontinuity in the torsion first derivatives are related to the matter distribution through the field equation. In addition, we develop a model that describes a flat FLRW model embedded in a 5-dimensional de Sitter or anti–de Sitter, where a 5-dimensional cosmological constant emerges from the torsion.

The activity of the soft gamma ray repeater SGR 1806-20 is studied in correlation with the EXPLORER and NAUTILUS data, during the year 2004, for gravitational wave (GW) short signal search. Corresponding to the most significant triggers, the bright outburst on October 5th and the giant flare (GF) on December 27th, the associated GW signature is searched. Two methods are employed for processing the data. With the average-modulus algorithm, the presence of short pulses with energy $E_{\mathrm{gw}}\ge 1.8\times {10}^{49}\mathrm{erg}$ is excluded with 90% probability, under the hypothesis of isotropic emission. This value is comparable to the upper limits obtained by LIGO regarding similar sources. Using the cross-correlation method, we find a discrepancy from the null-hypothesis of the order of 1%. This statistical excess is not sufficient to claim a systematic association between the gravitational and the electromagnetic radiations, because the estimated GW upper limits are yet several orders of magnitude far away from the theoretically predicted levels, at least three for the most powerful SGR flare.

We consider enhancing the sensitivity of future gravitational-wave detectors by using double optical spring. When the power, detuning and bandwidth of the two carriers are chosen appropriately, the effect of the double optical spring can be described as a “negative inertia,” which cancels the positive inertia of the test masses and thus increases their response to gravitational waves. This allows us to surpass the free-mass standard quantum limit (SQL) over a broad frequency band, through signal amplification, rather than noise cancellation, which has been the case for all broadband SQL-beating schemes so far considered for gravitational-wave detectors. The merit of such signal amplification schemes lies in the fact that they are less susceptible to optical losses than noise-cancellation schemes. We show that it is feasible to demonstrate such an effect with the Gingin High Optical Power Test Facility, and it can eventually be implemented in future advanced GW detectors.

In this paper, we report on the measurement of the rate of inclusive ${\pi }^0$ production induced by charged-current neutrino interactions in a ${\mathrm{C}}_8{\mathrm{H}}_8$ target at a mean energy of 1.3 GeV in the K2K near detector. Out of a sample of 11 606 charged-current neutrino interactions, we select 479 ${\pi }^0$ events with two reconstructed photons. We find that the cross section for the inclusive ${\pi }^0$ production relative to the charged-current quasielastic cross section is $\frac{{\sigma }_{\mathrm{CC}{\pi }^0}}{{\sigma }_{\mathrm{CCQE}}}=0.426\pm 0.032(\mathrm{stat})\pm 0.035(\mathrm{syst})$. The energy-dependent cross section ratio is also measured. The results are consistent with previous experiments for exclusive channels on different targets.

It has been known for some time that the well-established large mixing angle (LMA) solution to the observed solar neutrino deficit fails to predict a flat energy spectrum for Super-Kamiokande as opposed to what the data indicates. It also leads to a Chlorine rate which appears to be too high as compared to the data. We investigate the possible solution to these inconsistencies with nonstandard neutrino interactions, assuming that they come as extra contributions to the ${\nu }_{\alpha }{\nu }_{\beta }$ and ${\nu }_{\alpha }e$ vertices that affect both the propagation of neutrinos in the Sun and their detection. We find that, among the many possibilities for nonstandard couplings, only the diagonal imaginary ones lead to a solution to the tension between the LMA predictions and the data, implying neutrino instability in the solar matter. Unitarity requirements further restrict the solution and a neutrino decay into an antineutrino and a Majoron within the Sun is the one favored. Antineutrino probability is however too small to open the possibility of experimentally observing antineutrinos from the Sun due to NSI.

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the invariant differential cross section for production of $K_S^0$, $\omega$, ${\eta }^{\prime }$, and $\varphi$ mesons in $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$. Measurements of $\omega$ and $\varphi$ production in different decay channels give consistent results. New results for the $\omega$ are in agreement with previously published data and extend the measured $p_T$ coverage. The spectral shapes of all hadron transverse momentum distributions measured by PHENIX are well described by a Tsallis distribution functional form with only two parameters, $n$ and $T$, determining the high-$p_T$ and characterizing the low-$p_T$ regions of the spectra, respectively. The values of these parameters are very similar for all analyzed meson spectra, but with a lower parameter $T$ extracted for protons. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

We present an integral representation for the parity-even part of the two-loop six-point planar next-to-maximally helicity-violating amplitude in terms of Feynman integrals which have simple transformation properties under the dual conformal symmetry. We probe the dual conformal properties of the amplitude numerically, subtracting the known infrared divergences. We find that the subtracted amplitude is invariant under dual conformal transformations, confirming existing conjectures through two-loop order. We also discuss the all-loop structure of the six-point next-to-maximally helicity-violating amplitude and give a parametrization whose dual conformal invariant building blocks have a simple physical interpretation.

In this paper, we study the cosmological constant emerging from the Wheeler-DeWitt equation as an eigenvalue of the related Sturm-Liouville problem. We employ Gaussian trial functionals and we perform a mode decomposition to extract the transverse-traceless component, namely, the graviton contribution, at one loop. We implement a noncommutative-geometry–induced minimal length to calculate the number of graviton modes. As a result, we find regular graviton fluctuation energies for the Schwarzschild, de Sitter, and anti-de Sitter backgrounds. No renormalization scheme is necessary to remove infinities, in contrast to what happens in conventional approaches.

This is the second of two companion papers on computing the self-force in a radiation gauge; more precisely, the method uses a radiation gauge for the radiative part of the metric perturbation, together with an arbitrarily chosen gauge for the parts of the perturbation associated with changes in black-hole mass and spin and with a shift in the center of mass. In a test of the method delineated in the first paper, we compute the conservative part of the self-force for a particle in circular orbit around a Schwarzschild black hole. The gauge vector relating our radiation gauge to a Lorenz gauge is helically symmetric, implying that the quantity $h_{\alpha \beta }{u}^{\alpha }{u}^{\beta }$ must have the same value for our radiation gauge as for a Lorenz gauge; and we confirm this numerically to one part in ${10}^{14}$. As outlined in the first paper, the perturbed metric is constructed from a Hertz potential that is in a term obtained algebraically from the retarded perturbed spin-2 Weyl scalar, ${\psi }_0^{\mathrm{ret}}$. We use a mode-sum renormalization and find the renormalization coefficients by matching a series in $L=\ell +1/2$ to the large-$L$ behavior of the expression for the self-force in terms of the retarded field $h_{\alpha \beta }^{\mathrm{ret}}$; we similarly find the leading renormalization coefficients of $h_{\alpha \beta }{u}^{\alpha }{u}^{\beta }$ and the related change in the angular velocity of the particle due to its self-force. We show numerically that the singular part of the self-force has the form $f_{\alpha }^{\mathrm{S}}=⟨{\nabla }_{\alpha }{\rho }^{-1}⟩$, the part of ${\nabla }_{\alpha }{\rho }^{-1}$ that is axisymmetric about a radial line through the particle. This differs only by a constant from its form for a Lorenz gauge. It is because we do not use a radiation gauge to describe the change in black-hole mass that the singular part of the self-force has no singularity along a radial line through the particle and, at least in this example, is spherically symmetric to subleading order in $\rho$.

We study the self-gravitational effect on the equation of state (EoS) of Bose and Fermi gases in thermal equilibrium at the end of reheating, the period after quark-hadron transition and before big bang nucleosynthesis (BBN). After introducing new grand canonical partition functions based on the work of Uhlenbeck and Gropper, we notice some interesting features of the newly developed EoSs with distinct behaviors of relativistic and nonrelativistic gases under self-gravity. The usual negligence of the self-gravitational effect when solving the background expansion of the early Universe is justified with numerical results, showing the magnitude of the self-gravitational modification of the state constant to be less than $O({10}^{-78})$. This helps us to clarify the background thermal evolution of the primordial patch. Such clarification is crucial in testing gravity theories, evaluating inflation models and determining element abundances in BBN.

We present an example of a gauge-invariant Lagrangian that contains four derivatives and describes one massive, nonghostlike, degree of freedom.

We study the interplay between a soft muon Yukawa coupling generated radiatively with the trilinear $A$-terms of the minimal supersymmetric standard model (MSSM) and the anomalous magnetic moment of the muon. In the absence of a tree-level muon Yukawa coupling the lightest smuon mass is predicted to be in the range between 600 GeV and 2200 GeV at $2\sigma$, if the bino mass $M_1$ is below 1 TeV. Therefore, a detection of a smuon (in conjunction with a sub-TeV bino) at the LHC would directly imply a nonzero muon Yukawa coupling in the MSSM superpotential. Inclusion of slepton flavor mixing could in principle lower the mass of one smuonlike slepton below 600 GeV. However, the experimental bounds on radiative lepton decays instead strengthen the lower mass bound, with larger effects for smaller $M_1$, We also extend the analysis to the electron case and find that a light selectron close to the current experimental search limit may prove the MSSM electron Yukawa coupling to be nonzero.

In the present Universe visible and dark matter contribute comparable energy density although they have different properties. This phenomenon can be explained if the dark matter relic density, originating from a dark matter asymmetry, is fully determined by the baryon asymmetry. Thus the dark matter mass is not arbitrary; rather, it becomes predictive. We realize this scenario in baryon (lepton) number conserving models where two or more neutral singlet scalars decay into two or three baryonic (leptonic) dark matter scalars, and also decay into quarks (leptons) through other on-shell and/or off-shell exotic scalar bilinears. The produced baryon (lepton) asymmetries in the dark matter scalar and in the standard model quarks (leptons) are thus equal and opposite. The dark matter mass can be predicted in a range from a few GeV to a few TeV, depending on the baryon (lepton) numbers of the decaying scalars and the dark matter scalar. The dark matter scalar can interact with the visible matter through the exchange of the standard model Higgs boson, opening a window for the dark matter direct detection experiments. These models also provide testable predictions in the searches for the exotic scalar bilinears at LHC.

We report on our first experiences with a mixed action setup with overlap valence quarks and nonperturbatively $\mathrm{O}(a)$ improved Wilson sea quarks. For the latter we employ CLS $N_f=2$ configurations with light sea-quark masses at small lattice spacings. Exact chiral symmetry allows to consider very light valence quarks and explore the matching to (partially-quenched) Chiral Perturbation Theory (ChPT) in a mixed $ϵ/p$-regime. We compute the topological susceptibility and the low-lying spectrum of the massless Neuberger-Dirac operator for three values of the sea-quark mass, and compare the sea-quark mass dependence to NLO ChPT in the mixed regime. This provides two different determinations of the chiral condensate, as well as information about some NLOlow-energy couplings. Our results allow to test the consistency of the mixed-regime approach to ChPT, as well as of the mixed action framework.

Existence of the fourth family follows from the basics of the standard model (SM) and the actual mass spectrum of the third family fermions. We discuss possible manifestations of the fourth SM family at existing and future colliders. The LHC and Tevatron potentials to discover the fourth SM family have been compared. The scenario with dominance of the anomalous decay modes of the fourth-family quarks has been considered in detail.

In this work, we propose a nonresonant explanation for the $Y(4260)$ structure observed in the $e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-}$ process, i.e., $Y(4260)$ is not a genuine resonance. Our result indicates that the $Y(4260)$ structure can be reproduced by the interference of production amplitudes of the $e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-}$ processes via direct $e^{+}{e}^{-}$ annihilation and through intermediate charmonia $\psi (4160)/\psi (4415)$. Besides describing the $Y(4260)$ line shape in $e^{+}{e}^{-}\to J/\psi {\pi }^{+}{\pi }^{-}$ well, such a nonresonant explanation for the $Y(4260)$ structure naturally answers why there is no evidence of $Y(4260)$ in the exclusive open-charm decay channel and $R$-value scan.

We study the viability of generic Higgsless models at low energies when compliance with electroweak precision observables and unitarity constraints up to the TeV scale are imposed. Our analysis shows that consistency with $S$ and $T$ can be achieved at the one-loop level even with a single light vector state, $m_V\lesssim 500\mathrm{GeV}$. However, this scenario turns out to be strongly disfavored when direct resonance searches at the Tevatron are also taken into account. We show that a fully consistent picture can be obtained if an axial state is introduced. Interestingly, $m_V$ is still predicted to be light (below 1 TeV) while typical values of $m_A$ span over the window $1.2m_V\le m_A\le 1.4m_V$. Our results for the vector channel are rather robust and well within the reach of present-day colliders, while the axial channel is more loosely constrained.

The emission of $\nu \overline{\nu }$ pairs off electrons in a polarized ultraintense electromagnetic (e.g., laser) wave field is analyzed. We elaborate on the significance of nonlinear electrodynamics effects (i.e., multiphoton processes) and the peculiarities of neutrino production. Special attention is devoted to the convergence of the reaction probabilities as a function of the number of absorbed photons. Expressions for large field intensities are provided. The asymmetry between the probabilities of electron and $\mu +\tau$ neutrino production depends on initial conditions such as energy of the wave field photons and the field intensity. These findings differ from the lowest-order perturbative calculation of the reaction $\gamma +e\to e^{\prime }+\nu \overline{\nu }$.