We construct an exact time-dependent charged dilaton $C$ metric in four-dimensional $\mathcal{N}=4$ gauged supergravity. The scalar field drives the time evolution by transferring energy to the black holes, thereby causing their masses to increase and their acceleration to decrease. The values of the electric/magnetic and scalar charges determine three regions of potential time evolution. This solution holographically describes a strongly coupled three-dimensional conformal field theory on the background of an evolving black hole. We also find new static charged dilaton $C$ metrics, which arise in four-dimensional Einstein-Maxwell-dilaton theories whose scalar potential can be expressed in terms of a superpotential.

It was recently argued that $f(T)$ gravity could inherit “remnant symmetry” from the full Lorentz group, despite the fact that the theory is not locally Lorentz invariant. Confusion has arisen regarding the implication of this result for the previous works, which established that $f(T)$ gravity is pathological due to superluminal propagation, local acausality, and nonunique time evolution. We clarify that the existence of the “remnant group” does not rid the theory of these various problems but, instead, strongly supports it.

We describe a positive energy theorem for Einstein gravity coupled to scalar fields with first-derivative interactions, so-called $P(X,\varphi )$ theories. We offer two independent derivations of this result. The first method introduces an auxiliary field to map the theory to a Lagrangian describing two canonical scalar fields, where one can apply a positive energy result of Boucher and Townsend. The second method works directly at the $P(X,\varphi )$ level and uses spinorial arguments introduced by Witten. The latter approach follows that of recent work by Nozawa and Shiromizu [Phys. Rev. D 89, 023011 (2014)], but the end result is considerably less restrictive. We point to the technical step where our derivation deviates from theirs, which substantially expands the class of Lagrangians encompassed by the theorem. One of the more interesting implications of our analysis is to show it is possible to have positive energy in cases where dispersion relations following from locality and S-matrix analyticity are violated. This indicates that these two properties are logically distinct; i.e., it is possible to have positive energy even when the S-matrix is nonanalytic and vice versa.

We investigate laboratory tests of dark energy theories which modify gravity in a way generalizing the inverse power law chameleon models. We make use of the tomographic description of such theories which captures $f(R)$ models in the large curvature limit, the dilaton and the symmetron. We consider their effects in various experiments where the presence of a new scalar interaction may be uncovered. More precisely, we focus on the Casimir, Eötvös-Washington and neutron experiments. We show that dilatons, symmetrons and generalized chameleon models are efficiently testable in the laboratory. For generalized chameleons, we revise their status in the light of forthcoming Casimir experiments like CANNEX in Amsterdam and show that they are within reach of detection.

We study the production of sterile neutrinos in the early Universe from $\pi \to l{\nu }_s$ shortly after the QCD phase transition in the absence of a lepton asymmetry, while including finite-temperature corrections to the $\pi$ mass and decay constant $f_{\pi }$. Sterile neutrinos with masses $\lesssim 1\mathrm{MeV}$ produced via this mechanism freeze out at $T_f\simeq 10\mathrm{MeV}$ with a distribution function that is highly nonthermal and that features a sharp enhancement at low momentum, thereby making this species cold even for very light masses. Dark matter abundance constraints from the cosmic microwave background and phase space density constraints from the most dark-matter-dominated dwarf spheroidal galaxies provide upper and lower bounds, respectively, on combinations of mass and mixing angles. For $\pi \to \mu {\nu }_s$, the bounds lead to a narrow region of compatibility with the latest results from the 3.55-keV line. The nonthermal distribution function leads to free-streaming lengths (today) in the range of a few kpc, consistent with the observation of cores in dwarf galaxies. For sterile neutrinos with mass $\lesssim 1\mathrm{eV}$ that are produced by this reaction, the most recent accelerator and astrophysical bounds on $U_{ls}$ combined with the nonthermal distribution function suggests a substantial contribution from these sterile neutrinos to $N_{\text{eff}}$.

In general relativity gravitational waves propagate at the speed of light; however, in alternative theories of gravity that might not be the case. We investigate the effects of a modified speed of gravity, $c_T^2$, on the $B$ modes of the cosmic microwave background (CMB) anisotropy in polarization. We find that a departure from the light speed value would leave a characteristic imprint on the BB spectrum part induced by tensors, manifesting as a shift in the angular scale of its peaks which allows us to constrain $c_T$ without any significant degeneracy with other cosmological parameters. We derive constraints from current data and forecast the accuracy with which $c_T$ will be measured by the next generation CMB satellites. In the former case, using the available Planck and BICEP2 data sets, we obtain $c_T^2=1.30\pm 0.79$ and $c_T^2<2.85$ at 95% C.L. by assuming a power law primordial tensor power spectrum and $c_T^2<2.33$ at 95% C.L. if the running of the spectral index is allowed. More interestingly, in the latter case we find future CMB satellites capable of constraining $c_T^2$ at percent level, comparable with bounds from binary pulsar measurements, largely due to the absence of degeneracy with other cosmological parameters.

The Fermi-LAT Collaboration has studied the gamma-ray emission from a stacked population of dwarf spheroidal galaxies and used this information to set constraints on the dark matter annihilation cross section. Interestingly, their analysis uncovered an excess with a test statistic (TS) of 8.7. If interpreted naively, this constitutes a $2.95\sigma$ local excess ($p‐\text{value}=0.003$), relative to the expectations of their background model. In order to further test this interpretation, the Fermi-LAT team studied a large number of blank sky locations and found $\mathrm{TS}>8.7$ excesses to be more common than predicted by their background model, decreasing the significance of their dwarf excess to $2.2\sigma (p‐\text{value}=0.027)$. We argue that these $\mathrm{TS}>8.7$ blank sky locations are largely the result of unresolved blazars, radio galaxies, and star-forming galaxies, and show that multiwavelength information can be used to reduce the degree to which such sources contaminate the otherwise blank sky. In particular, we show that masking regions of the sky that lie within 1° of sources contained in the BZCAT or CRATES catalogs reduce the fraction of blank sky locations with $\mathrm{TS}>8.7$ by more than a factor of 2. Taking such multiwavelength information into account can enable experiments such as Fermi to better characterize their backgrounds and increase their sensitivity to dark matter in dwarf galaxies, the most important of which remain largely uncontaminated by unresolved point sources. We also note that for the range of dark matter masses and annihilation cross sections currently being tested by studies of dwarf spheroidal galaxies, simulations predict that Fermi should be able to detect a significant number of dark matter subhalos. These subhalos constitute a population of subthreshold gamma-ray point sources and represent an irreducible background for searches for dark matter annihilation in dwarf galaxies.

We show that the Standard Model electroweak interaction of ultrarelativistic electrons with nucleons (the $eN$ interaction) in a neutron star (NS) permeated by a seed large-scale helical magnetic field provides its growth up to $\gtrsim 10^{15}\mathrm{G}$ during a time comparable with the ages of young magnetars $\sim 10^4\mathrm{yr}$. The magnetic field instability originates from the parity violation in the $eN$ interaction entering the generalized Dirac equation for right and left massless electrons in an external uniform magnetic field. We calculate the average electric current given by the solution of the modified Dirac equation containing an extra current for right and left electrons (positrons), which turns out to be directed along the magnetic field. Such a current includes both a changing chiral imbalance of electrons and the $eN$ potential given by a constant neutron density in a NS. Then we derive the system of the kinetic equations for the chiral imbalance and the magnetic helicity which accounts for the $eN$ interaction. By solving this system, we show that a sizable chiral imbalance arising in a neutron protostar due to the Urca process $e_{\mathrm{L}}^{-}+p\to N+{\nu }_{\mathrm{eL}}$ diminishes very rapidly because of a huge chirality-flip rate. Thus the $eN$ term prevails over the chiral effect, providing a huge growth of the magnetic helicity and the helical magnetic field.

Radiative decays of $X(3872)$ are studied in single-channel approximation (SCA) and in the coupled-channel (CC) approach, where the decay channels $D{\overline{D}}^{*}$ are described with the string-breaking mechanism. In SCA the transition rate ${\tilde{\mathrm{\Gamma }}}_2=\mathrm{\Gamma }(2{{}^{3}P}_1\to \psi \gamma )=71.8\mathrm{keV}$ and large ${\tilde{\mathrm{\Gamma }}}_1=\mathrm{\Gamma }(2{{}^{3}P}_1\to J/\psi \gamma )=85.4\mathrm{keV}$ are obtained, giving for their ratio the value $\widetilde{R_{\psi \gamma }}=\frac{{\tilde{\mathrm{\Gamma }}}_2}{{\tilde{\mathrm{\Gamma }}}_1}=0.84$. In the CC approach, three factors are shown to be equally important: First, the admixture of the $1{{}^{3}P}_1$ component in the normalized wave function of $X(3872)$ due to the CC effects. Its weight $c_{\mathrm{X}}(E_{\mathrm{R}})=0.200\pm 0.015$ is calculated. Second, the use of the multipole function $g(r)$ instead of $r$ in the overlap integrals, determining the partial widths. Third, the choice of the gluon-exchange interaction for $X(3872)$, as well as for other states above threshold. If for $X(3872)$ the gluon-exchange potential is taken to be the same as for low-lying charmonium states, then in the CC approach ${\mathrm{\Gamma }}_1=\mathrm{\Gamma }(X(3872)\to J/\psi \gamma )\sim 3\mathrm{keV}$ is very small, giving the large ratio $R_{\psi \gamma }=\frac{\mathcal{B}(X(3872)\to \psi (2S)\gamma )}{\mathcal{B}(X(3872)\to J/\psi \gamma )}\gg 1.0$. Arguments are presented why the gluon-exchange interaction may be suppressed for $X(3872)$ and in this case ${\mathrm{\Gamma }}_1=42.7\mathrm{keV}$, ${\mathrm{\Gamma }}_2=70.5\mathrm{keV}$, and $R_{\psi \gamma }=1.65$ are predicted for the minimal value $c_{\mathrm{X}}(\min )=0.185$, while for the maximal value $c_{\mathrm{X}}=0.215$ we obtain ${\mathrm{\Gamma }}_1=30.8\mathrm{keV}$, ${\mathrm{\Gamma }}_2=73.2\mathrm{keV}$, and $R_{\psi \gamma }=2.38$, which agrees with the LHCb data.

We use AdS/QCD to analyze the quark and gluon scalar and pseudoscalar condensates around static color sources described by a circular Wilson loop. We also derive the static dipole-dipole interactions between rectangular Wilson loops in AdS/QCD and discuss their relevance for static string interactions in QCD at strong coupling.

We present Dalitz plot analyses for the decays of $B$ mesons to $D^{-}{D}^0{K}^{+}$ and ${\overline{D}}^0{D}^0{K}^{+}$. We report the observation of the $D_{s1}^{*}(2700{)}^{+}$ resonance in these two channels and obtain measurements of the mass $M(D_{s1}^{*}(2700{)}^{+})={2699}_{-7}^{+14}\mathrm{MeV}/c^2$ and of the width $\mathrm{\Gamma }(D_{s1}^{*}(2700{)}^{+})={127}_{-19}^{+24}\mathrm{MeV}$, including statistical and systematic uncertainties. In addition, we observe an enhancement in the $D^0{K}^{+}$ invariant mass around $2350–2500\mathrm{MeV}/c^2$ in both decays $B^0\to D^{-}{D}^0{K}^{+}$ and $B^{+}\to {\overline{D}}^0{D}^0{K}^{+}$, which we are not able to interpret. The results are based on $429{\mathrm{fb}}^{-1}$ of data containing $471\times 10^{6}B\overline{B}$ pairs collected at the $\mathrm{\Upsilon }(4S)$ resonance with the BABAR detector at the SLAC National Accelerator Laboratory.

Evidence of a heavy neutrino, ${\nu }_H$, in the $K^{+}\to {\mu }^{+}{\nu }_H$ decays was sought using the E949 experimental data with an exposure of $1.70\times 10^{12}$ stopped kaons. With the major background from the radiative $K^{+}\to {\mu }^{+}{\nu }_{\mu }\gamma$ decay understood and suppressed, upper limits (90% C.L.) on the neutrino mixing matrix element between the muon and heavy neutrinos, $|U_{\mu H}{|}^2$, were set at the level of $10^{-7}$ to $10^{-9}$ for the heavy neutrino mass region 175 to $300\mathrm{MeV}/c^2$.

Bose symmetry and $CPT$ symmetry are two very fundamental symmetries of nature. However, the validity of these symmetries in diverse phenomena must be verified by experiments. We propose new techniques to probe these two fundamental symmetries in the realm of mesons by using the Dalitz plot of a few three-body meson decays. Since these symmetries are very fundamental in nature, their violations, if any, are expected to be extremely small. Hence, observing their violations requires study of a huge data sample. In this context we introduce a new three-dimensional plot which we refer to as the Dalitz “prism.” This provides an innovative means for acquiring the huge statistics required for such studies. Using the Dalitz plots and the Dalitz prisms we chart out the way to probe the violations of Bose and $CPT$ symmetries in a significant manner. Since mesons are unstable and composite particles, testing the validity of Bose symmetry and the $CPT$ symmetry in these cases is of paramount importance for fundamental physics.

We derive the three loop soft function for inclusive Higgs production in gluon fusion, and use it to perform the resummation of the Higgs cross section at ${\mathrm{N}}^3{\mathrm{LL}}^{\prime }$ in soft-collinear effective theory. We improve the accuracy of the resummation by including contributions of collinear origin. We include finite top, bottom and charm mass effect where available. These results are available through the public code ResHiggs.

We report the first observation of $B^0\to X(3872)(K^{+}{\pi }^{-})$ and evidence for $B^{+}\to X(3872)(K^0{\pi }^{+})$. We measure the product of branching fractions for the former to be $\mathcal{B}(B^0\to X(3872)(K^{+}{\pi }^{-}))\times \mathcal{B}(X(3872)\to J/\psi {\pi }^{+}{\pi }^{-})=(7.9\pm 1.3(\text{stat})\pm 0.4(\text{syst}))\times 10^{-6}$ and find that $B^0\to X(3872)K^{*}(892{)}^0$ does not dominate the $B^0\to X(3872)K^{+}{\pi }^{-}$ decay mode. We also measure $\mathcal{B}(B^{+}\to X(3872)(K^0{\pi }^{+}))\times \mathcal{B}(X(3872)\to J/\psi {\pi }^{+}{\pi }^{-})=(10.6\pm 3.0(\text{stat})\pm 0.9(\text{syst}))\times 10^{-6}$. This study is based on the full data sample of $711{\mathrm{fb}}^{-1}$ ($772\times 10^{6}B\overline{B}$ pairs) collected at the $\mathrm{{\rm Y}}(4S)$ resonance with the Belle detector at the KEKB collider.

In this note we construct asymptotically Lifshitz spacetimes in the Chern-Simons formulation of three-dimensional higher spin gravity and relate the resulting theories to integrable systems which are elements of the KdV hierarchy.

We describe the observed light-baryon spectrum by extending superconformal quantum mechanics to the light front and its embedding in AdS space. This procedure uniquely determines the confinement potential for arbitrary half-integer spin. To this end, we show that fermionic wave equations in AdS space are dual to light-front supersymmetric quantum-mechanical bound-state equations in physical space-time. The specific breaking of conformal invariance explains hadronic properties common to light mesons and baryons, such as the observed mass pattern in the radial and orbital excitations, from the spectrum generating algebra. The holographic embedding in AdS also explains distinctive and systematic features, such as the spin-$J$ degeneracy for states with the same orbital angular momentum, observed in the light-baryon spectrum.

We construct the new one-dimensional Dirac Hamiltonians that are spectrally isomorphic (not isospectral) with the known exactly solvable models. Explicit formulas for their spectra and eigenstates are provided. The operators are utilized for the description of Dirac fermions in graphene in the presence of an inhomogeneous electromagnetic field. We discuss explicit, physically relevant, examples of spectrally isomorphic systems with both nonperiodic and periodic electromagnetic barriers. In the latter case, spectrally isomorphic two- and three-gap systems associated with the Ablowitz-Kaup-Newell-Segur hierarchy are considered.