We determined the critical exponent $\nu$ of the scalar $O(N)$ model with a strategy based on the definition of the correlation length in the infrared limit. The functional renormalization group treatment of the model shows that there is an infrared fixed point in the broken phase. The appearing degeneracy induces a dynamical length scale there, which can be considered as the correlation length. It is shown that the IR scaling behavior can account either for the Ising type phase transition in the three-dimensional $O(N)$ model, or for the Kosterlitz-Thouless type scaling of the two-dimensional $O(2)$ model.

We present the complete set of analytical solutions of the geodesic equation in the five-dimensional Myers-Perry space-time with equal rotation parameter in terms of the Weierstraß’s elliptic and Weierstraß’s zeta and sigma functions. We study the underlying polynomials in the polar and radial equations which depend on the parameters of the metric and conserved quantities of a test particle and characterize the motion by their zeros. We exemplify the efficiency of the analytical method on the orbits of test particles.

We compute the accuracy at which a Laser Interferometer Space Antenna-like space-based gravitational wave detector will be able to observe deviations from general relativity in the low frequency approximation. To do so, we introduce six correction parameters that account for modified gravity in the second post-Newtonian gravitational wave phase for inspiralling supermassive black hole binaries with spin precession on quasicircular orbits. Our implementation can be regarded as a subset of the parametrized post-Einsteinian formalism developed by Yunes and Pretorius, being able to investigate also next-to-leading order effects. In order to find error distributions for the alternative theory parameters, we use the Fisher information formalism and carry out Monte Carlo simulations for 17 different binary black hole mass configurations in the range ${10}^5{M}_{\odot }<M<{10}^8{M}_{\odot }$ with ${10}^3$ randomly distributed points in the parameter space each, comparing the full (FWF) and restricted (RWF) versions of the gravitational waveform. We find that the binaries can roughly be separated into two groups: one with low ($\lesssim {10}^7{M}_{\odot }$) and one with high total masses ($\gtrsim {10}^7{M}_{\odot }$). The RWF errors on the alternative theory parameters are 2 orders of magnitude higher than the FWF errors for high-mass binaries while almost comparable for low-mass binaries. Because of dilution of the available information, the accuracy of the binary parameters is reduced by factors of a few, except for the luminosity distance, which is affected more seriously in the high-mass regime. As an application as well as to compare our research with previous work, we compute an optimal lower bound on the graviton Compton wavelength, which is increased by a factor of $\sim 1.6$ when using the FWF.

In this paper, we analyze the phase transition phenomena in Born-Infeld anti-de Sitter (BI AdS) black holes using Ehrenfest’s scheme of standard thermodynamics. The critical points are marked by the divergences in the heat capacity. In order to investigate the nature of the phase transition, we analytically check both Ehrenfest equations near the critical points. Our analysis reveals that this is indeed a second order phase transition. Finally, we analyze the nature of the phase transition using the state space geometry approach. This is found to be compatible with Ehrenfest’s scheme.

Black-hole–neutron-star (BHNS) binary mergers can form disks in which magnetorotational instability (MRI)-induced turbulence may drive accretion onto the remnant BH, supporting relativistic jets and providing the engine for a short-hard gamma-ray burst (SGRB). Our earlier study of magnetized BHNSs showed that NS tidal disruption winds the magnetic field into a toroidal configuration, with poloidal fields so weak that capturing MRI with full-disk simulations would require $\sim {10}^8$ CPU hours. In that study we imposed equatorial symmetry, suppressing poloidal magnetic fields that might be generated from plasma crossing the orbital plane. Here we show that initial conditions that break this symmetry (i.e., tilted poloidal magnetic fields in the NS) generate much stronger poloidal fields in the disk, indicating that asymmetric initial conditions may be necessary for establishing BHNS mergers as SGRB progenitors via fully general relativistic magnetohydrodynamic simulations. We demonstrate that BHNS mergers may form an SGRB engine under the right conditions by seeding the remnant disk from an unmagnetized BHNS simulation with purely poloidal fields dynamically unimportant initially, but strong enough to resolve MRI. Magnetic turbulence occurs in the disk, driving accretion and supporting Poynting-dominated jet outflows sufficient to power an SGRB.

We present a detailed analysis (including redshift tomography) of the cosmic dipoles in the $\mathrm{Keck}+\mathrm{VLT}$ quasar absorber and in the Union2 SnIa samples. We show that the fine structure constant cosmic dipole obtained through the $\mathrm{Keck}+\mathrm{VLT}$ quasar absorber sample at $4.1\sigma$ level is anomalously aligned with the corresponding dark energy dipole obtained through the Union2 sample at $2\sigma$ level. The angular separation between the two dipole directions is $11.3°\pm 11.8°$. We use Monte Carlo simulations to find the probability of obtaining the observed dipole magnitudes with the observed alignment, in the context of an isotropic cosmological model with no correlation between dark energy and fine structure constant $\alpha$. We find that this probability is less than one part in ${10}^6$. We propose a simple physical model (extended topological quintessence) which naturally predicts a spherical inhomogeneous distribution for both dark energy density and fine structure constant values. The model is based on the existence of a recently formed giant global monopole with Hubble scale core which also couples nonminimally to electromagnetism. Aligned dipole anisotropies would naturally emerge for an off-center observer for both the fine structure constant and for dark energy density. This model smoothly reduces to $\Lambda \mathrm{CDM}$ for proper limits of its parameters. Two predictions of this model are (a) a correlation between the existence of strong cosmic electromagnetic fields and the value of $\alpha$ and (b) the existence of a dark flow on Hubble scales due to the repulsive gravity of the global defect core (“Great Repulser”) aligned with the dark energy and $\alpha$ dipoles. The direction of the dark flow is predicted to be towards the spatial region of lower accelerating expansion. Existing data about the dark flow are consistent with this prediction.

Motivated by the complex gamma-ray spectrum of the Galactic Center source now measured over five decades in energy, we revisit the issue of the role of dark matter (DM) annihilations in this interesting region. We reassess whether the emission measured by the HESS collaboration could be a signature of dark matter annihilation, and we use the Fermi LAT spectrum to model the emission from SgrA*, using power-law spectral fits. We find that good fits are achieved by a power law with an index $\sim 2.5–2.6$, in combination with a spectrum similar to the one observed from pulsar population and with a spectrum from a $\gtrsim 10\mathrm{TeV}$ DM annihilating to a mixture of $b\overline{b}$ and harder ${\tau }^{+}{\tau }^{-}$ channels and with boost factors of the order of a hundred. Alternatively, we also consider the combination of a log-parabola fit with the DM contribution. Finally, as both the spectrum of gamma rays from the Galactic Center and the spectrum of cosmic ray electrons exhibit a cutoff at TeV energies, we study the dark matter fits to both data sets. Constraining the spectral shape of the purported dark matter signal provides a robust way of comparing data. We find a marginal overlap only between the 99.999% C.L. regions in parameter space.

Neutrino oscillations in Earth matter may introduce peculiar modulations in supernova (SN) neutrino spectra. The detection of this effect has been proposed as a diagnostic tool for the neutrino mass hierarchy at a large 1–3 leptonic mixing angle, ${\theta }_{13}$. We perform an updated study on the observability of this effect at large next-generation underground detectors (i.e., 0.4 Mton water Cherenkov, 50 kton scintillation, and 100 kton liquid argon detectors) based on neutrino fluxes from state-of-the-art SN simulations and accounting for statistical fluctuations via Monte Carlo simulations. Since the average energies predicted by recent simulations are lower than previously expected, and a tendency towards the equalization of the neutrino fluxes appears during the SN cooling phase, the detection of the Earth matter effect will be more challenging than expected from previous studies. We find that none of the proposed detectors shall be able to detect the Earth modulation for the neutrino signal of a typical galactic SN at 10 kpc. It should be observable in a 100 kton liquid argon detector for a SN at a few kpc, and all three detectors would clearly see the Earth signature for very close-by stars only ($d\sim 0.2\mathrm{kpc}$). Finally, we show that adopting IceCube as a codetector together with a Mton water Cherenkov detector is not a viable option either.

The recently announced Higgs boson discovery marks the dawn of the direct probing of the electroweak symmetry breaking sector. Sorting out the dynamics responsible for electroweak symmetry breaking now requires probing the Higgs boson interactions and searching for additional states connected to this sector. In this work, we analyze the constraints on Higgs boson couplings to the standard model gauge bosons using the available data from Tevatron and LHC. We work in a model-independent framework expressing the departure of the Higgs boson couplings to gauge bosons by dimension-six operators. This allows for independent modifications of its couplings to gluons, photons, and weak gauge bosons while still preserving the Standard Model (SM) gauge invariance. Our results indicate that best overall agreement with data is obtained if the cross section of Higgs boson production via gluon fusion is suppressed with respect to its SM value and the Higgs boson branching ratio into two photons is enhanced, while keeping the production and decays associated to couplings to weak gauge bosons close to their SM prediction.

The $CP$-violating version of the Minimal Supersymmetric Standard Model is an example of a model where experimental data do not preclude the presence of light Higgs bosons in the range around 10–110 GeV. Such light Higgs bosons, decaying almost wholly to $b\overline{b}$ pairs, may be copiously produced at the LHC but would remain inaccessible to conventional Higgs searches because of intractable QCD backgrounds. We demonstrate that a significant number of these light Higgs bosons would be boosted strongly enough for the pair of daughter $b$-jet pairs to appear as a single ‘fat’ jet with substructure. Tagging such jets could extend the discovery potential at the LHC into the hitherto-inaccessible region for light Higgs bosons.

I consider variations in the definitions, at next-to-leading order and at next-to-next-to leading order, of a general-mass variable flavor number scheme (GM-VFNS) for heavy flavor structure functions. I also define a new “optimal” scheme choice improving the smoothness of the transition from one flavor number to the next. I investigate the variation of the structure function for a fixed set of parton distribution functions (PDFs) and also the change in the PDFs when a new MSTW2008-type global fit to data is performed for each GM-VFNS. At next-to-leading order the parton distributions, and predictions using them at hadron colliders, can vary by $\sim 2–3\%$ from the mean value. At next-to-next-to leading order there is far more stability with varying GM-VFNS definitions, and changes in PDFs and predictions are less than 1%, with most variations at very small $x$ values. Hence, mass-scheme variation is an additional and significant source of uncertainty when considering parton distributions, but as with all perturbative uncertainties, it diminishes quickly as higher orders are included.

In this work, we study six tree-dominated $B\to a_1(1260)a_1(1260)$ and $b_1(1235)b_1(1235)$ decays in the perturbative QCD (pQCD) approach, where $a_1$ ($b_1$) is a ${}^{3}P_1$ (${}^{1}P_1$) axial-vector meson. Based on the perturbative calculations and phenomenological analysis, we find that (a) the $CP$-averaged branching ratio of $B^0\to a_1^{+}{a}_1^{-}$ decay in the pQCD approach is $54.7\times {10}^{-6}$, which agrees well with the current data and the predictions given in the QCD factorization approach within errors; (b) the numerical results for the decay rates of the other five channels are found to be in the order of ${10}^{-6}$ to ${10}^{-5}$, which could be accessed at $B$ factories and Large Hadron Collider experiments; (c) other physical observables such as polarization fractions and direct $CP$-violating asymmetries are also investigated with the pQCD approach in the present work and the predictions can be confronted with relevant experiments in the near future; (d) the different phenomenologies shown between $B\to a_1{a}_1$ and $B\to b_1{b}_1$ decays are expected to be tested by the ongoing Large Hadron Collider and forthcoming SuperB experiments, which could shed light on the typical QCD dynamics involved in these decay modes, as well as in ${}^{3}P_1$ meson $a_1$ and ${}^{1}P_1$ meson $b_1$.

Under the assumption that the dijet excess seen by the CDF Collaboration near 150 GeV in $Wjj$ production is due to the lightest technipion of the low-scale technicolor (LSTC) process ${\rho }_T\to W{\pi }_T$, we study its observability in LHC detectors for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. We describe interesting new kinematic tests that can provide independent confirmation of this LSTC hypothesis. We show that cuts similar to those employed by CDF, and recently by ATLAS, cannot confirm the dijet signal. We propose cuts tailored to the LSTC hypothesis and its backgrounds at the LHC that may reveal ${\rho }_T\to \ell \nu jj$. Observation of the isospin-related channel ${\rho }_T^{\pm }\to Z{\pi }_T^{\pm }\to {\ell }^{+}{\ell }^{-}jj$ and of ${\rho }_T^{\pm }\to WZ$ in the ${\ell }^{+}{\ell }^{-}{\ell }^{\pm }{\nu }_{\ell }$ and ${\ell }^{+}{\ell }^{-}jj$ modes will be important confirmations of the LSTC interpretation of the CDF signal. The $Z{\pi }_T$ channel is experimentally cleaner than $W{\pi }_T$ and its rate is known from $W{\pi }_T$ by phase space. It can be discovered or excluded with the collider data expected by the end of 2012. The $WZ\to 3\ell \nu$ channel is cleanest of all and its rate is determined from $W{\pi }_T$ and the LSTC parameter $\sin \chi$. This channel and $WZ\to {\ell }^{+}{\ell }^{-}jj$ are discussed as a function of $\sin \chi$.

We perform a global fit of the parameters of the Standard Model with a sequential fourth generation (SM4) to LHC and Tevatron Higgs data and electroweak precision data. Using several likelihood ratio tests, we compare the performance of the SM4 and the Standard Model (SM3) at describing the measured data. Since the SM3 and SM4 are not nested (i.e., the SM3 cannot be considered as a special case of the SM4 with some parameters fixed), the usual analytical formulae for $p$-values in likelihood ratio tests do not hold. We thus apply a new method to compute these $p$-values. For a Higgs mass of 126.5 GeV and fourth-generation quark masses above 600 GeV, we find that the SM4 is excluded at $3.1\sigma$.

Distributions sensitive to the underlying event are studied in events containing one or more charged-particle jets produced in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect $800\mu {\mathrm{b}}^{-1}$ of data taken during 2010. Jets are reconstructed using the anti-$k_t$ algorithm with radius parameter $R$ varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle $p_{\mathrm{T}}$ are measured as functions of $p_{\mathrm{T}}^{\mathrm{jet}}$ in regions transverse to and opposite the leading jet for $4\mathrm{GeV}<p_{\mathrm{T}}^{\mathrm{jet}}<100\mathrm{GeV}$. In addition, the $R$ dependence of the mean values of these observables is studied. In the transverse region, both the multiplicity and the scalar sum of the transverse momentum at fixed $p_{\mathrm{T}}^{\mathrm{jet}}$ vary significantly with $R$, while the average charged-particle transverse momentum has a minimal dependence on $R$. Predictions from several Monte Carlo tunes have been compared to the data; the predictions from Pythia 6, based on tunes that have been determined using LHC data, show reasonable agreement with the data, including the dependence on $R$. Comparisons with other generators indicate that additional tuning of soft-QCD parameters is necessary for these generators. The measurements presented here provide a testing ground for further development of the Monte Carlo models.

We present the first numerical implementation of the minimal Landau background gauge for Yang-Mills theory on the lattice. Our approach is a simple generalization of the usual minimal Landau gauge and is formulated for the general SU(N) gauge group. We also report on preliminary tests of the method in the four-dimensional SU(2) case, using different background fields. Our tests show that the convergence of the numerical minimization process is comparable to the case of a null background. The uniqueness of the minimizing functional employed is briefly discussed.

In neutrinophilic two-Higgs-doublet models, neutrinos acquire mass due to a Higgs field with vacuum expectation value of the order of $\simeq {10}^{-2}\mathrm{eV}$, corresponding to a Compton wavelength in the $10\mu \mathrm{m}$ range. This creates a situation in which nonminimal couplings between Higgs fields and spacetime curvature may lead to novel observable effects. Among these, we discuss the possibility of variable neutrino masses, with implications for the dependence of the neutrino oscillation frequency on the spacetime curvature, a further source of dispersion of the neutrino arrival times from supernovae events, and possibly also a mechanism leading to gravitationally-induced neutrino superluminality. Finally, we propose laboratory-scale experiments in which properly designed electroweak cavities may be used to change neutrino masses, which should be observable through time of flight experiments.

The Pomeranchuk instability, in which an isotropic Fermi surface distorts and becomes anisotropic due to strong interactions, is a possible mechanism for the growing number of experimental systems which display transport properties that differ along the $x$ and $y$ axes. We show here that the gauge-gravity duality can be used to describe such an instability in fermionic systems. Our holographic model consists of fermions in a background which describes the causal propagation of a massive neutral spin-two field in an asymptotically anti–de Sitter spacetime. The Fermi surfaces in the boundary theory distort spontaneously and become anisotropic once the neutral massive spin-two field develops a normalizable mode in the bulk. Analysis of the fermionic correlators reveals that the low-lying fermionic excitations are non-Fermi liquidlike both before and after the Fermi surface shape distortion. Further, the spectral weight along the Fermi surface is angularly dependent and can be made to vanish along certain directions.

Nonextremal solution with warped resolved-deformed conifold background is important to study the infrared limit of large $N$ thermal QCD. Earlier works in this direction have not taken into account all the backreactions on the geometry, namely from the branes, fluxes, and black-hole carefully. In the present work we make some progress in this direction by solving explicitly the supergravity equations of motions in the presence of the backreaction from the black hole. The backreactions from the branes and the fluxes on the other hand and to the order that we study, are comparatively suppressed. Our analysis reveal, among other things, how the resolution parameter would depend on the horizon radius and how the renormalization group flows of the coupling constants should be understood in these scenarios, including their effects on the background three-form fluxes. We also study the effect of switching on a chemical potential in the background and, in a particularly simplified scenario, compute the actual value of the chemical potential for our case.

We construct $\mathcal{N}=1$ supergravity extensions of scalar field theories with higher-derivative kinetic terms. Special attention is paid to the auxiliary fields, whose elimination leads not only to corrections to the kinetic terms, but to new expressions for the potential energy as well. For example, a potential energy can be generated even in the absence of a superpotential. Our formalism allows one to write a supergravity extension of any higher-derivative scalar field theory and therefore has applications to both particle physics and cosmological model building. As an illustration, we couple the higher-derivative Dirac-Born-Infeld action describing a 3-brane in six dimensions to $\mathcal{N}=1$ supergravity. This displays a number of new features including the fact that in the regime where the higher-derivative kinetic terms become important, the potential tends to be everywhere negative.