An improved Tsallis statistics is implemented in a multisource thermal model to describe systematically pseudorapidity spectra of charged particles produced in relativistic nucleon-nucleon ($pp$ or $p\overline{p}$) collisions at various collision energies and in relativistic nucleus-nucleus ($AA$) collisions at different energies with different centralities. The results with Tsallis statistics using the two-cylindrical multisource thermal model are in good agreement with the experimental data measured at RHIC and LHC energies. It is found that the rapidity shifts of longitudinal sources increase linearly with collision energies and centralities in the framework. According to the laws, we also give a prediction of the pseudorapidity distributions in $pp(\overline{p})$ collisions at higher energies.

Several intriguing aspects of neutrino oscillation phenomenology like the origin of small neutrino masses, the absolute neutrino mass scale, the neutrino mass hierarchy, i.e., normal or inverted, and the nature of neutrinos, i.e., Dirac or Majorana, etc. have been addressed from a general perspective. We show how the fundamental considerations of unitary transformations, naturalness, and the seesaw mechanism suffice to determine the texture structure of fermion Yukawa couplings and discuss the significance of the effective mass in $0\nu \beta \beta$ decay for the texture structure of these couplings.

The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be observed with rather simple setups. The direction of the electric field induced by this emission process depends only on the local magnetic field vector and on the incoming direction of the air shower. We report on measurements of the electric field vector where, in addition to this geomagnetic component, another component has been observed that cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric field component is polarized radially with respect to the shower axis, in agreement with predictions made by Askaryan who described radio emission from particle showers due to a negative charge excess in the front of the shower. Our results are compared to calculations which include the radiation mechanism induced by this charge-excess process.

We look at solutions [both Bogomol’nyi-Prasad-Sommerfield (BPS) and non-BPS] of the $\mathbb{C}{\mathbb{P}}^{N-1}$ model on $\mathbb{R}\times S^1$ (with twisted boundary conditions), in particular by using a conformal mapping technique, and we show how to interpret these solutions by decomposing them into expressions describing constituent solitons. We point out the problems that may arise (for non-BPS solutions) when one naively looks at the clustering properties of these solutions. This could lead to misunderstandings when studying extrapolations between small and large compactification radii.

We investigate the structure of gravitational self-interactions of coherently oscillating axions in the general relativistic framework. A generic action for a massive scalar field in the Friedmann-Robertson-Walker background is first introduced based on the effective field theory approach to cosmological perturbations. Using the obtained setup, we evaluate the effective gravitational interaction of the massive scalar field, i.e. scalar quartic interactions mediated by metric perturbations. Applying the results to the system of dark matter axions, we estimate their self-interaction rate and discuss its implications for the axion Bose-Einstein condensate dark matter scenario. Leading contributions for the gravitational interactions of axions are given by the process mediated by the dynamical graviton field, which is essentially the Newtonian potential induced by fluctuations of the background fluids. We find that it leads to the same order of magnitude for the interaction rate of dark matter axions in the condensed regime, compared with the results of previous studies using the Newtonian approximation.

Despite the extraordinary attention that modified gravity theories have attracted over the past decade, the geodesic deviation equation in this context has not received proper formulation thus far. This equation provides an elegant way to investigate the timelike, null and spacelike structure of spacetime geometries. In this investigation we provide the full derivation of this equation in situations where general relativity has been extended in Robertson-Walker background spacetimes. We find that for null geodesics the contribution arising from the geometrical new terms is in general nonzero. Finally we apply the results to a well-known class of $f(R)$ theories, compare the results with general relativity predictions and obtain the equivalent area distance relation.

The main goal of the LISA Pathfinder (LPF) mission is to fully characterize the acceleration noise models and to test key technologies for future space-based gravitational-wave observatories similar to the eLISA concept. The data analysis team has developed complex three-dimensional models of the LISA Technology Package (LTP) experiment onboard the LPF. These models are used for simulations, but, more importantly, they will be used for parameter estimation purposes during flight operations. One of the tasks of the data analysis team is to identify the physical effects that contribute significantly to the properties of the instrument noise. A way of approaching this problem is to recover the essential parameters of a LTP model fitting the data. Thus, we want to define the simplest model that efficiently explains the observations. To do so, adopting a Bayesian framework, one has to estimate the so-called Bayes factor between two competing models. In our analysis, we use three main different methods to estimate it: the reversible jump Markov chain Monte Carlo method, the Schwarz criterion, and the Laplace approximation. They are applied to simulated LPF experiments in which the most probable LTP model that explains the observations is recovered. The same type of analysis presented in this paper is expected to be followed during flight operations. Moreover, the correlation of the output of the aforementioned methods with the design of the experiment is explored.

Gravitational waves emitted by black-hole binary systems have the highest signal-to-noise ratio in LIGO and Virgo detectors when black-hole spins are aligned with the orbital angular momentum and extremal. For such systems, we extend the effective-one-body inspiral-merger-ringdown waveforms to generic mass ratios and spins calibrating them to 38 numerical-relativity nonprecessing waveforms produced by the SXS Collaboration. The numerical-relativity simulations span mass ratios from 1 to 8, spin magnitudes up to 98% of extremality, and last for 40 to 60 gravitational-wave cycles. When the total mass of the binary is between 20 and $200M_{\odot }$, the effective-one-body nonprecessing (dominant mode) waveforms have overlap above 99% (using the advanced-LIGO design noise spectral density) with all of the 38 nonprecessing numerical waveforms, when maximizing only on initial phase and time. This implies a negligible loss in event rate due to modeling. We also show that—without further calibration— the precessing effective-one-body (dominant mode) waveforms have overlap above 97% with two very long, strongly precessing numerical-relativity waveforms, when maximizing only on the initial phase and time.

Multicomponent dark matter particles may have a more intricate direct detection signal than simple elastic scattering on nuclei. In a broad class of well-motivated models, the inelastic excitation of dark matter particles is followed by de-excitation via $\gamma$ decay. In experiments with fine energy resolution, such as many $0\nu 2\beta$ decay experiments, this motivates a highly model-independent search for the sidereal daily modulation of an unexpected $\gamma$ line. Such a signal arises from a two-step weakly interacting massive particle (WIMP) interaction: the WIMP is first excited in the lead shielding and subsequently decays back to the ground state via the emission of a monochromatic $\gamma$ within the detector volume. We explore this idea in detail by considering the model of magnetic inelastic WIMPs and take a sequence of CUORE-type detectors as an example. We find that under reasonable assumptions about detector performance it is possible to efficiently explore mass splittings of up to a few hundred keV for a WIMP of weak-scale mass and transitional magnetic moments. The modulation can be cheaply and easily enhanced by the presence of additional asymmetric lead shielding. We devise a toy simulation to show that a specially designed asymmetric shielding may result in up to 30% diurnal modulations of the two-step WIMP signal, leading to additional strong gains in sensitivity.

Topological objects of $SU(3)$ gluodynamics are studied at the infrared scale near the transition temperature with the help of zero and near-zero modes of the overlap Dirac operator. We construct UV filtered topological charge densities corresponding to three versions of the temporal boundary condition applied to this operator, for which the zero mode is known to be located on corresponding three constituent dyons (antidyons) in the reference case of an analytical (anti)caloron solution. The clustering of the three topological charge densities marks the positions of three types of dyons and antidyons which can therefore be considered as present in equilibrium (Monte Carlo) gluonic fields at the given resolution scale. We classify them either as constituents of nondissociated (anti)calorons or as constituents of (anti)dyon pairs or as isolated (anti)dyons. The pattern of the Polyakov loop describing the centers and the interior of these clusters is observed after a limited number of overimproved cooling steps and resembles the description known from analytical caloron solutions.

We investigate the effect of the medium on the thermal conductivity of a pion gas out of chemical equilibrium by solving the relativistic transport equation in the Chapman-Enskog and relaxation time approximations. Using an effective model for the $\pi \pi$ cross section involving $\rho$ and $\sigma$ meson exchange, medium effects are incorporated through thermal one-loop self-energies. The temperature dependence of the thermal conductivity is observed to be significantly affected.

It is well known that understanding the structure of jet radiation can significantly improve Higgs analyses. Using Fox-Wolfram moments we systematically study the geometric patterns of additional jets in weak boson fusion Higgs production with a decay to photons. First, we find a significant improvement with respect to the standard analysis based on an analysis of the tagging jet correlations. In addition, we show that replacing a jet veto by a Fox-Wolfram moment analysis of the extra jet radiation almost doubles the signal-to-background ratio. Finally, we show that this improvement can also be achieved based on a modified definition of the Fox-Wolfram moments which avoids introducing a new physical scale below the factorization scale. This modification can reduce the impact of theory uncertainties on the Higgs rate and couplings measurements.

Recent theoretical developments in gravitational physics have motivated experimental searches for violations of Newton’s inverse square law of gravity at small separations. There has also been considerable theoretical and experimental progress in establishing the Casimir effect. These two classes of experiments and others in fundamental physics measure the forces between polycrystalline metals at micron-order separations, and are thus susceptible to forces due to electrostatic patch fields on their surfaces. We develop the theory for the patch force power spectra which provides the necessary tools to estimate the magnitude of random patch signals. We apply our results to two experiments intending to measure nonNewtonian gravitational signals using the isoelectronic technique where the mean effect of patches is nullified by design but random patch signals may still spoil the measurement sensitivity. Our results help gauge the sensitivity limitations of real experimental setups and the analytical formulas we derive suggest useful strategies for engineering and minimizing undesired patch effects in future experiments.

We examine the effective low-energy theory of the adjoint sector of Dirac gaugino models and its UV completions, and identify the main source of tuning. A holomorphic scalar adjoint mass square (the “$b_M$ term”) is generated at the same order (one-loop) as the Dirac gaugino mass (the “$m_D$ term”), leading to the problematic relation $b_M\sim 16{\pi }^2{m}_D^2$, somewhat analogous to the $\mu -B_{\mu }$ problem of gauge mediation. We identify the leading operators of the low-energy effective theory contributing to the adjoint sector, and evaluate them in various UV completions, confirming the existence of this problem. We suggest a solution by introducing messenger mixing and tuning the relevant parameters. We also present a novel dynamical model for Dirac gauginos based on a strongly coupled supersymmetric (SUSY) QCD theory, where the additional adjoint $M$ is identified with a confined meson, the U(1) with a baryon number-like symmetry, and the messengers with the confined baryons. We find a SUSY-breaking vacuum with a nonvanishing $D$ term, which after tuning the messenger mixing angles gives rise to a realistic gaugino and squark sector.

Scattering lengths for two pseudoscalar meson systems, $\pi \pi (I=2)$, $KK(I=1)$ and $\pi K(I=3/2,1/2)$, are calculated from lattice QCD by using the finite size formula. We perform the calculation with $N_f=2+1$ gauge configurations generated on $32^3\times 64$ lattice using the Iwasaki gauge action and a nonperturbatively $\mathcal{O}(a)$-improved Wilson action at $a^{-1}=2.19\mathrm{GeV}$. The quark masses correspond to $m_{\pi }=0.17–0.71\mathrm{GeV}$. For the $\pi K(I=1/2)$ system, we use the variational method with the two operators, $\overline{s}u$ and $\pi K$, to separate the contamination from the higher states. In order to obtain the scattering length at the physical quark mass, we fit our results at several quark masses with the formula of the $\mathcal{O}(p^4)$ chiral perturbation theory and that includes the effects of the discretization error from the Wilson fermion, Wilson chiral perturbation theory. We found that the mass dependence of our results near $m_{\pi }=0.17\mathrm{GeV}$ are described well by Wilson chiral perturbation theory but not by chiral perturbation theory. The scattering lengths at the physical point are given as $a_0^{(2)}{m}_{\pi }=-0.04263(22)(41)$, $a_0^{(1)}{m}_K=-0.310(17)(32)$, $a_0^{(3/2)}{\mu }_{\pi K}=-0.0469(24)(20)$, and $a_0^{(1/2)}{\mu }_{\pi K}=0.142(14)(27)$. Possible systematic errors are also discussed.

We compute three-point functions for the $SL(2,\mathbb{R})$-WZNW model. After reviewing the case of the two-point correlator, we compute spectral flow preserving and nonpreserving correlation functions in the space-time picture involving three vertex operators carrying an arbitrary amount of spectral flow. When only one or two insertions have nontrivial spectral flow numbers, the method we employ allows us to find expressions without any constraint on the spin values. Unlike these cases, the same procedure restrains the possible spin configurations when the three vertices belong to nonzero spectral flow sectors. We perform several consistency checks on our results. In particular, we verify that they are in complete agreement with previously computed correlators involving states carrying a single unit of spectral flow.

We construct a holographic two-band superconductor model with interband Josephson coupling. We investigate the effects the Josephson coupling has on the superconducting condensates and the critical temperature for their formation numerically, as well as analytically where possible. We calculate the ac conductivity and find it qualitatively similar to the single band superconductor. We investigate the nodal structure of our holographic two-band superconductor from the low temperature behavior of the thermal conductivity and find it nodeless.

We investigate the decay of a quantum electrodynamical (QED) vacuum in arbitrary space-dependent electric fields. In particular, we analyze the resonance peaks of the positron emission spectrum for the external fields with subcycle structure. For this, we study the transmission probability in the framework of the scattering approach to vacuum pair production. In an under-the-barrier scattering regime, we show that the width of a transmission resonance can be enhanced when the effective scattering potential contains multiple wells. Such a broadening in the resonance width corresponds to a decrease in the tunneling time. This may be relevant for observing the vacuum decay at shorter time scales before the external field is adiabatically turned off. In an above-the-barrier scattering regime, we give a set of coupled differential equations for the numerical computation of the Bogoliubov coefficients.

The Skyrme model has a natural generalization amenable to a standard Hamiltonian treatment, consisting of the standard sigma model and the Skyrme terms, a potential, and a certain term sextic in first derivatives. Here we demonstrate that, in this theory, each pair of terms in the static energy functional which may support topological solitons according to the Derrick criterion (i.e., each pair of terms with opposite Derrick scaling) separately possesses a topological energy bound. As a consequence, there exists a four-parameter family of topological bounds for the full generalized Skyrme model. The optimal bounds, i.e., the optimal values of the parameters, depend both on the form of the potential and on the relative strength of the different terms. It also follows that various submodels of the generalized Skyrme model have one-parameter families of topological energy bounds. We also consider the case of topological bounds for the generalized Skyrme model on a compact base space as well as generalizations to higher dimensions.