Dynamic AdS/QCD is a holographic model of strongly coupled gauge theories with the dynamics included through the running anomalous dimension of the quark bilinear, $\gamma$. We apply it to describe the physics of massive quarks in the conformal window of $\mathrm{SU}(N_c)$ gauge theories with $N_f$ fundamental flavors, assuming the perturbative two-loop running for $\gamma$. We show that to find regular, holographic renormalization group flows in the infrared, the decoupling of the quark flavors at the scale of the mass is important, and enact it through suitable boundary conditions when the flavors become on shell. We can then compute the quark condensate and the mesonic spectrum $(M_{\rho },M_{\pi },M_{\sigma })$ and decay constants. We compute their scaling dependence on the quark mass for a number of examples. The model matches perturbative expectations for large quark mass and naïve dimensional analysis (including the anomalous dimensions) for small quark mass. The model allows study of the intermediate regime where there is an additional scale from the running of the coupling, and we present results for the deviation of scalings from assuming only the single scale of the mass.

We propose a new antenna configuration of a torsion-bar antenna (TOBA) and study its performance. A TOBA is a novel type of an antenna for low-frequency gravitational waves (GWs) which consists of two bar-shaped orthogonal test masses. Previously only the rotation of the bars on the horizontal plane had been considered as an output signal. In this paper, we introduce a new antenna configuration for a TOBA to incorporate two additional outputs by measuring the rotation of the bars on the vertical planes. Such a triple-output TOBA can be regarded as a network of three coincident but misaligned interferometric detectors. The target sensitivity we consider in this paper is about $3\times 10^{-20}{\mathrm{Hz}}^{-1/2}$ at 1 Hz. Since the triple-output TOBA is sensitive to all directions of GWs, event detection rates are improved by a factor of 1.7. It also increases the parameter resolution drastically for short-duration observations because the triple-output TOBA has three independent output signals and can discriminate two polarization modes of a short-duration GW signal even with single antenna. For instance, in the case of a $10^4\text{−}10^4$ IMBH merger at 100 Mpc, the source location is typically measurable with an accuracy of $\pm 0.01\text{−}0.1$ steradians which is roughly two order of magnitude better than the conventional single-output TOBA.

We consider a class of nonlocal, pure-metric modified gravity models which were developed to reproduce the Tully-Fisher relation without dark matter and without changing the amount of weak lensing predicted by general relativity. Previous work gave only the weak field limiting form of the field equations specialized to a static and spherically symmetric geometry. Here we derive the full field equations and specialize them to a homogeneous, isotropic and spatially flat geometry. We also discuss the problem of fitting the free function to reproduce the expansion history. Results are derived for models in which the MOND acceleration $a_0\approx 1.2\times 10^{-10}\mathrm{m}.{\mathrm{s}}^{-2}$ is a fundamental constant and for the more phenomenologically interesting case in which the MOND acceleration changes with the cosmological expansion rate.

We investigate the motion of spinning test bodies in General Relativity. By means of a multipolar approximation method for extended test bodies we derive the equations of motion and classify the orbital motion of pole-dipole test bodies in the equatorial plane of the Kerr geometry. An exact expression for the periastron shift of a spinning test body is given. Implications of test body spin corrections are studied and compared with the results obtained by means of other approximation schemes.

We study the gravitational collapse of a generalized Vaidya spacetime in the context of the cosmic censorship hypothesis. We develop a general mathematical framework to study the conditions on the mass function so that future directed nonspacelike geodesics can terminate at the singularity in the past. Thus our result generalizes earlier works on gravitational collapse of the combinations of Type-I and Type-II matter fields. Our analysis shows transparently that there exist classes of generalized Vaidya mass functions for which the collapse terminates with a locally naked central singularity. We calculate the strength of these singularities to show that they are strong curvature singularities and there can be no extension of spacetime through them.

We derive an integro-differential equation for propagation of cosmological gravitation waves in spatially closed cosmology whereas the traceless transverse tensor part of the anisotropic stress tensor is free-streaming neutrinos (including antineutrinos), which have been traveling essentially without collision since temperature dropped below about $10^{10}\mathrm{K}$. We studied the short wavelengths and long wavelengths of gravitational waves (GWs) that enter the horizon in closed spacetime. The solution shows that the anisotropic stress reduces the squared amplitude by 76% for wavelengths that enter the horizon during radiation-dominated phase and this reduction is less for the wavelength that enters the horizon at later times. At the end we compare the results to the flat case and then we investigate the dependence of the evolution of GWs on cosmological parameters.

The observational evidence for the acceleration of the Universe demonstrates that canonical theories of cosmology and particle physics are incomplete, if not incorrect, and that new physics is out there, waiting to be discovered. Forthcoming high-resolution ultrastable spectrographs will play a crucial role in this quest for new physics, by enabling a new generation of precision consistency tests. Here we focus on astrophysical tests of the stability of nature’s fundamental couplings, and by using principal component analysis techniques further calibrated by existing VLT data we discuss how the improvements that can be expected with ESPRESSO and ELT-HIRES will impact on fundamental cosmology. In particular we show that a 20 to 30 night program on ELT-HIRES will allow it to play a leading role in fundamental cosmology.

We address the issue of how many $e$-folds we would naturally expect if inflation occurred at an energy scale of order ${10}^{16}\mathrm{GeV}$. We use the canonical measure on trajectories in classical phase space, specialized to the case of flat universes with a single scalar field. While there is no exact analytic expression for the measure, we are able to derive conditions that determine its behavior. For a quadratic potential $V(\varphi )=m^2{\varphi }^2/2$ with $m=2\times {10}^{13}\mathrm{GeV}$ and cutoff at $M_{\text{Pl}}=2.4\times {10}^{18}\mathrm{GeV}$, we find an expectation value of $2\times {10}^{10}$ $e$-folds on the set of Friedmann-Robertson-Walker trajectories. For cosine inflation $V(\varphi )={\mathrm{\Lambda }}^4[1-\cos (\varphi /f)]$ with $f=1.5\times {10}^{19}\mathrm{GeV}$, we find that the expected total number of $e$-folds is 50, which would just satisfy the observed requirements of our own Universe; if $f$ is larger, more than 50 $e$-folds are generically attained. We conclude that one should expect a large amount of inflation in large-field models and more limited inflation in small-field (hilltop) scenarios.

The late time accelerated expansion of the Universe demands that even in local galactic scales it is desirable to study astrophysical phenomena, particularly relativistic accretion related phenomena in massive galaxies or in galaxy mergers and the dynamics of the kiloparsecs-scale structure and beyond, in the local galaxies in Schwarzschild–de Sitter (SDS) background, rather than in Schwarzschild or Newtonian paradigm. Owing to the complex and nonlinear character of the underlying magnetohydrodynamical equations in general relativistic (GR) regime, it is quite useful to have a Newtonian analogous potential containing all the important GR features that allows us to treat the problem in Newtonian framework for study of accretion and its related processes. From the principle of conserved Hamiltonian of the test particle motion, here, a three dimensional Newtonian analogous potential has been obtained in spherical geometry corresponding to SDS/Schwarzschild–anti–de Sitter spacetime, that reproduces almost all of the GR features in its entirety with remarkable accuracy. The derived potential contains an explicit velocity dependent term of the test particle that renders an approximate relativistic modification of Newtonian-like potential. The complete orbital dynamics around SDS geometry and the epicyclic frequency corresponding to SDS metric have been extensively studied in the Newtonian framework using the derived potential. Applying the derived analogous potential it is found that the current accepted value of $\mathrm{\Lambda }\sim {10}^{-56}{\mathrm{cm}}^{-2}$ moderately influences both sonic radius as well as Bondi accretion rate, especially for spherical accretion with smaller values of adiabatic constant and temperature, which might have interesting consequences on the stability of accretion disk in active galactic nuclei/radio galaxies.

In this work, we implement a complex scalar dark matter (DM) candidate in a ${U(1)}_{B-L}$ gauge extension of the Standard Model. The model contains three right-handed neutrinos with different quantum numbers and a rich scalar sector, with extra doublets and singlets. In principle, these extra scalars can have vacuum expectation values ($V_{\mathrm{\Phi }}$ and $V_{\varphi }$ for the extra doublets and singlets, respectively) belonging to different energy scales. In the context of $\zeta \equiv \frac{V_{\mathrm{\Phi }}}{V_{\varphi }}\ll 1$, which allows one to obtain naturally light active neutrino masses and mixing compatible with neutrino experiments, the DM candidate arises by imposing a $Z_2$ symmetry on a given complex singlet, ${\varphi }_2$, in order to make it stable. After doing a study of the scalar potential and the gauge sector, we obtain all the DM-dominant processes concerning the relic abundance and direct detection. Then, for a representative set of parameters, we find that a complex DM with mass around 200 GeV, for example, is compatible with the current experimental constraints without resorting to resonances. However, additional compatible solutions with heavier masses can be found in vicinities of resonances. Finally, we address the issue of having a light $CP$-odd scalar in the model showing that it is safe concerning the Higgs and the $Z_{\mu }$-boson invisible decay widths, and also astrophysical constraints regarding energy loss in stars.

Evidence for an excess of gamma rays with $\mathcal{\text{O}}(\mathrm{GeV})$ energy coming from the center of our galaxy has been steadily accumulating over the past several years. Recent studies of the excess in data from the Fermi telescope have cast doubt on an explanation for the excess arising from unknown astrophysical sources. A potential source of the excess is the annihilation of dark matter into standard model final states, giving rise to gamma ray production. The spectrum of the excess is well fit by 30 GeV dark matter annihilating into a pair of $b$ quarks with a cross section of the same order of magnitude as expected for a thermal relic. Simple models that can lead to this annihilation channel for dark matter are in strong tension with null results from direct detection experiments. We construct a renormalizable model where dark matter-standard model interactions are mediated by a pseudoscalar that mixes with the $CP$-odd component of a pair of Higgs doublets, allowing for the gamma ray excess to be explained while suppressing the direct detection signal. We consider implications for this scenario from Higgs decays, rare $B$ meson decays and monojet searches and also comment on some difficulties that any dark matter model explaining the gamma ray excess via direct annihilation into quarks will encounter.

We present a comparative and systematic study of the fine-tuning in Higgs sectors in three scale-invariant next-to-minimal supersymmetric standard model (NMSSM) models: the first is the standard $Z_3$-invariant NMSSM; the second is the NMSSM plus additional matter filling $3(5+\overline{5})$ representations of $SU(5)$ and is called the $\mathrm{NMSSM}+$; while the third model comprises $4(5+\overline{5})$ and is called the $\mathrm{NMSSM}++$. Naively, one would expect the fine-tuning in the plus-type models to be smaller than that in the NMSSM since the presence of extra matter relaxes the perturbativity bound on $\lambda$ at the low scale. This, in turn, allows larger tree-level Higgs mass and smaller loop contribution from the top squarks. However we find that LHC limits on the masses of sparticles, especially the gluino mass, can play an indirect, but vital, role in controlling the fine-tuning. In particular, working in a semiconstrained framework at the grand unified theory scale, we find that the masses of third generation top squarks are always larger in the plus-type models than in the NMSSM without extra matter. This is a renormalization group equation effect which cannot be avoided, and as a consequence the fine-tuning in the $\mathrm{NMSSM}+$ ($\mathrm{\Delta }\sim 200$) is significantly larger than in the NMSSM ($\mathrm{\Delta }\sim 100$), with fine-tuning in the $\mathrm{NMSSM}++$ ($\mathrm{\Delta }\sim 600$) being significantly larger than in the $\mathrm{NMSSM}+$.

We present a calculation of soft-gluon corrections in flavor-changing neutral current top-quark production via anomalous $t$-$q$-$g$ couplings. The soft anomalous dimension matrix is explicitly calculated at one-loop accuracy. This calculation allows threshold resummation at next-to-leading-logarithm accuracy. We also derive expressions for the soft-gluon corrections at next-to-leading order and at next-to-next-to-leading order.

The angular distribution of the phase space arising in two-particle emission reactions induced by electrons and neutrinos is computed in the laboratory (Lab) system by boosting the isotropic distribution in the center of mass (CM) system used in Monte Carlo generators. The Lab distribution has a singularity for some angular values, coming from the Jacobian of the angular transformation between CM and Lab systems. We recover the formula we obtained in a previous calculation for the Lab angular distribution. This is in accordance with the Monte Carlo method used to generate two-particle events for neutrino scattering [J. T. Sobczyk, Phys. Rev. C 86, 015504 (2012)]. Inversely, by performing the transformation to the CM system, it can be shown that the phase-space function, which is proportional to the two-particle-two-hole (2p-2h) hadronic tensor for a constant current operator, can be computed analytically in the frozen nucleon approximation, if Pauli blocking is absent. The results in the CM frame confirm our previous work done using an alternative approach in the Lab frame. The possibilities of using this method to compute the hadronic tensor by a boost to the CM system are analyzed.

We show that the form of the recently proposed subleading soft graviton and gluon theorems in any dimension are severely constrained by elementary arguments based on Poincaré and gauge invariance as well as a self-consistency condition arising from the distributional nature of scattering amplitudes. Combined with the assumption of a local form as it would arise from a Ward identity the orbital part of the subleading operators is completely fixed by the leading universal Weinberg soft pole behavior. The polarization part of the differential subleading soft operators in turn is determined up to a single numerical factor for each hard leg at every order in the soft momentum expansion. In four dimensions, factorization of the Lorentz group allows us to fix the subleading operators completely.

We investigate the possibility of an ultraviolet (UV) zero in the $n$-loop beta function of a $\lambda ({\overrightarrow{\varphi }}^2{)}^2$ field theory with an $N$-component scalar field, $\overrightarrow{\varphi }$, in four spacetime dimensions, up to the level of $n=5$ loops. Although the two-loop beta function has a UV zero, we find that the $n$-loop beta function for $n=3$, 4, 5 either does not have a UV zero or does not have one at a value of $\lambda$ in approximate agreement with the two-loop calculation. Similar results are obtained after application of scheme transformations to the beta function and via calculation of Padé approximants. We thus conclude that in the range of $\lambda$ where the perturbative calculation of the $n$-loop beta function is reliable, the theory does not exhibit robust evidence of a UV zero up to the level of $n=5$ loops.

In this work we consider kink-antikink collisions for some classes of (1,1)-dimensional nonlinear models. We are particularly interested to investigate in which aspect the presence of a general kinetic content in the Lagrangian could be revealed in a collision process. We consider a particular class of models known as twin theories, where different models lead to the same solutions for the equations of motion and the same energy density profile. The theories can be distinguished in the level of the linear stability of a defect structure We study a class of k-defect theories depending on a parameter $M$, which is the twin theory of the usual ${\varphi }^4$ theory with standard dynamics. For $M\to \infty$, both models are characterized by the same potential. In the regime $1/M^2\ll 1$, we obtain analytically the spectrum of excitations around the kink solution. It is shown that with increasing the parameter $1/M^2$ (i) the gap between the zero mode and the first-excited mode increases, and (ii) the tendency of a one-bounce collision between the kink antikink increases. We numerically investigate kink-antikink scattering, looking for the influence of the parameter changing for the thickness and number of two-bounce windows and confronting the results with our analytical findings.