The approximate homogeneity of spatial sections of the Universe is well supported observationally, but the inhomogeneity of the spatial sections is even better supported. Here, we consider the implications of inhomogeneity in dust models for the connectedness of spatial sections at early times. We consider a nonglobal Lemaître-Tolman-Bondi (LTB) model designed to match observations, a more general, heuristic model motivated by the former, and two specific, global LTB models. We propose that the generic class of solutions of the Einstein equations projected back in time from the spatial section at the present epoch includes subclasses in which the spatial section evolves (with increasing time) smoothly (i) from being disconnected to being connected, or (ii) from being simply connected to being multiply connected, where the coordinate system is comoving and synchronous. We show that (i) and (ii) each contain at least one exact solution. These subclasses exist because the Einstein equations allow nonsimultaneous big bang times. The two types of topology evolution occur over time slices that include significantly postquantum epochs if the bang time varies by much more than a Planck time. In this sense, it is possible for cosmic topology evolution to be “mostly” classical.

We consider reheating driven by volume modulus decays in the LARGE volume scenario. Such reheating always generates nonzero dark radiation through the decays to the axion partner, while the only competitive visible sector decays are Higgs pairs via the Giudice-Masiero term. In the framework of sequestered models where the cosmological moduli problem is absent, the simplest model with a shift-symmetric Higgs sector generates $1.56\le \Delta N_{\mathrm{eff}}\le 1.74$. For more general cases, the known experimental bounds on $\Delta N_{\mathrm{eff}}$ strongly constrain the parameters and matter content of the models.

We develop and demonstrate an acceleration of the Liu and Tegmark quadratic estimator formalism for inverse variance foreground subtraction and power spectrum estimation in 21 cm tomography from $\mathcal{O}(N^3)$ to $\mathcal{O}(N\log N)$, where $N$ is the number of voxels of data. This technique makes feasible the megavoxel scale analysis necessary for current and upcoming radio interferometers by making only moderately restrictive assumptions about foreground models and survey geometry. We exploit iterative and Monte Carlo techniques and the symmetries of the foreground covariance matrices to quickly estimate the 21 cm brightness temperature power spectrum, $P(k_{\parallel },k_{\perp })$, the Fisher information matrix, the error bars, the window functions, and the bias. We also extend the Liu and Tegmark foreground model to include bright point sources with known positions in a way that scales as $\mathcal{O}[(N\log N)\times (N\mathrm{\text{point sources}})]\le \mathcal{O}(N^{5/3})$. As a first application of our method, we forecast error bars and window functions for the upcoming 128-tile deployment of the Murchinson Widefield Array, showing that 1000 hours of observation should prove sufficiently sensitive to detect the power spectrum signal from the Epoch of Reionization.

We assess the detectability of the gravitational wave signals from highly eccentric compact binaries. We use a simple model for the inspiral, merger, and ringdown of these systems. The model is based on mapping the binary to an effective single black hole system described by a Kerr metric, thereby including certain relativistic effects such as zoom-whirl-type behavior. The resultant geodesics source quadrupolar radiation and, in turn, are evolved under its dissipative effects. At the light ring, we attach a merger model that was previously developed for quasicircular mergers but also performs well for eccentric mergers with little modification. We apply this model to determine the detectability of these sources for initial, Enhanced, and Advanced laser interferometer gravitational-wave observatory across the parameter space of nonspinning close capture compact binaries. We conclude that, should these systems exist in nature, the vast majority will be missed by conventional burst searches or by quasicircular waveform templates in the advanced detector era. Other methods, such as eccentric templates or, more practically, a stacked excess power search, must be developed to avoid losing these sources. These systems would also have been missed frequently in the initial laser interferometer gravitational-wave observatory data analysis. Thus, previous null coincidence results with detected gamma-ray bursts cannot exclude the possibility of coincident gravitational wave signals from eccentric binaries.

Several $B$ and $B_s$ decays have been observed that have been cited as evidence for exchange ($E$), penguin annihilation ($PA$), and annihilation ($A$) processes, such as $\overline{b}d\to \overline{u}u$, $\overline{b}s\to \overline{u}u$, and $\overline{b}u\to W^{*}\to \overline{c}s$, respectively. These amplitudes are normally thought to be suppressed, as they involve the spectator quark in the weak interaction and thus should be proportional to the $B$-meson decay constant $f_B$. However, as pointed out a number of years ago, they can also be generated by rescattering from processes whose amplitudes do not involve $f_B$, such as color-favored tree amplitudes. In this paper we investigate a number of processes such as $B^0\to K^{+}{K}^{-}$, $B_s\to {\pi }^{+}{\pi }^{-}$, and $B^{+}\to D_s^{+}\varphi$, and identify promising states from which they can be generated by rescattering. We find that $E$-and $PA$-type processes are characterized, respectively, by amplitudes ranging from 5% to 10% and from 15% to 20% with respect to the largest amplitude from which they can rescatter. Based on this regularity, using approximate flavor SU(3) symmetry in some cases and time-reversal invariance in others, we predict the branching fractions for a large number of as-yet-unseen $B$ and $B_s$ decays in an extensive range from order ${10}^{-9}$ to ${10}^{-4}$.

LHC experiments have placed strong bounds on the production of supersymmetric colored particles (squarks and gluinos), under the assumption that all flavors of squarks are nearly degenerate. However, the current experimental constraints on stop squarks are much weaker, due to the smaller production cross section and difficult backgrounds. While light stops are motivated by naturalness arguments, it has been suggested that such particles become nearly impossible to detect near the limit where their mass is degenerate with the sum of the masses of their decay products. We show that this is not the case, and that searches based on missing transverse energy (${\mathrm{E̸}}_T$) have significant reach for stop masses above 175 GeV, even in the degenerate limit. We consider direct pair production of stops, decaying to invisible lightest supersymmetric particles (LSPs) and tops with either hadronic or semileptonic final states. Modest intrinsic differences in ${\mathrm{E̸}}_T$ are magnified by boosted kinematics and by shape analyses of ${\mathrm{E̸}}_T$ or suitably chosen observables related to ${\mathrm{E̸}}_T$. For these observables we show that the distributions of the relevant backgrounds and signals are well described by simple analytic functions, in the kinematic regime where signal is enhanced. Shape analyses of ${\mathrm{E̸}}_T$-related distributions will allow the LHC experiments to place significantly improved bounds on stop squarks, even in scenarios where the stop-LSP mass difference is degenerate with the top mass. Assuming $20{\mathrm{fb}}^{-1}$ of luminosity at $\sqrt{s}=8\mathrm{TeV}$, we conservatively estimate that experiments can exclude or discover degenerate stops with masses as large as $\sim 360\mathrm{GeV}$, and 560 GeV for massless LSPs.

We consider a model for a $Z^{\prime }$-boson coupled only to baryon minus lepton number and hypercharge. Besides the usual right-handed neutrinos, we add a pair of fermions with a fractional lepton charge, which we therefore call leptinos. One of the leptinos is taken to be odd under an additional $Z_2$ charge, the other even. This allows for a natural (inverse) seesaw mechanism for neutrino masses. The odd leptino is a candidate for dark matter, but has to be resonantly annihilated by the $Z^{\prime }$-boson or the Higgs-boson responsible for giving mass to the former. Considering collider and cosmological bounds on the model, we find that the $Z^{\prime }$-boson and/or the extra Higgs-boson can be seen at the LHC. With more pairs of leptinos leptogenesis is possible.

We study the charged Higgs production at LHC via its associated production with the top quark. The kinematic cuts are optimized to suppress the background processes so that the reconstruction of the charged Higgs and top quark is possible. The angular distributions with respect to top quark spin are explored to study the $Htb$ interaction at LHC.

We study two-color QCD with two flavors of Wilson fermion as a function of quark chemical potential $\mu$ and temperature $T$. We find evidence of a superfluid phase at intermediate $\mu$ and low $T$ where the quark number density and diquark condensate are both very well described by a Fermi sphere of nearly free quarks disrupted by a BCS condensate. Our results suggest that the quark contribution to the energy density is negative (and balanced by a positive gauge contribution), although this result is highly sensitive to details of the energy renormalization. We also find evidence that the chiral condensate in this region vanishes in the massless limit. This region gives way to a region of deconfined quark matter at higher $T$ and $\mu$, with the deconfinement temperature, determined from the renormalized Polyakov loop, decreasing only very slowly with increasing chemical potential. The quark number susceptibility ${\chi }_q$ does not exhibit any qualitative change at the deconfinement transition. We argue that this is because ${\chi }_q$ is not an appropriate measure of deconfinement for two-color QCD at high density.

We determine the energy-dependent amplitude for elastic $\pi \pi$ $P$-wave scattering in isospin-1 by computing part of the discrete energy spectrum of QCD in finite cubic boxes. We observe a rapidly rising phase shift that can be well described by a single $\rho$ resonance. The spectrum is obtained from hadron correlators computed using lattice QCD with light quark masses corresponding to $m_{\pi }\sim 400\mathrm{MeV}$. Variational analyses are performed with large bases of hadron interpolating fields including, as well as fermion bilinears that resemble $q\overline{q}$ constructions, also operators that resemble pairs of pions with definite relative and total momentum. We compute the spectrum for a range of center-of-mass momenta and in various irreducible representations of the relevant symmetry group. Hence we determine more than 30 values of the isospin-1 $P$-wave scattering phase shift in the elastic region, mapping out its energy dependence in unprecedented detail.

In this work we evaluate the $B$-meson drag and diffusion coefficients in a hot medium constituted of light mesons ($\pi$, $K$, $\overline{K}$, and $\eta$). We treat the $B$-meson and $B^{*}$-meson interactions with pseudo-Goldstone bosons in chiral perturbation theory at next-to-leading order within the constraints from heavy quark symmetry and employ standard unitarization techniques of next-to-leading order amplitudes in order to account for dynamically generated resonances (leading to a more efficient heavy-flavor diffusion) and thus reach higher temperatures. We estimate individual meson contributions from the gas to the transport coefficients and perform a comparison with other findings in literature. We report a bottom relaxation length of about 80 fm at a temperature of 150 MeV and for typical momenta of 1 GeV, at which our approach is reliable. Compared to a charm relaxation length of 40 fm in the same conditions, we conclude that the $B$ mesons provide a cleaner probe of the early stages of a heavy-ion collision.

We compare recent, seemingly different, approaches to transverse momentum dependent factorization (due to Echevarria, Idilbi, and Scimemi and to Collins), and show that they are the same, apart from an apparent difference in their definition of the $\overline{\mathrm{MS}}$ renormalization scheme.

We present a measurement of the $B^{+}\to \omega {\ell }^{+}\nu$ branching fraction based on a sample of 467 million $B\overline{B}$ pairs recorded by the BABAR detector at the SLAC PEP-II $e^{+}{e}^{-}$ collider. We observe $1125\pm 131$ signal decays, corresponding to a branching fraction of $\mathcal{B}(B^{+}\to \omega {\ell }^{+}\nu )=(1.21\pm 0.14\pm 0.08)\times {10}^{-4}$, where the first error is statistical and the second is systematic. The dependence of the decay rate on $q^2$, the invariant mass squared of the leptons, is compared to QCD predictions of the form factors based on a quark model and light-cone sum rules.

We have made a precise measurement of the absolute branching fractions of $B_s^0\to D_s^{(*)+}{D}_s^{(*)-}$ decays using $121.4{\mathrm{fb}}^{-1}$ of data recorded by the Belle experiment running at the ${\rm Y}(5S)$ resonance. The results are $\mathcal{B}(B_s^0\to D_s^{+}{D}_s^{-})=({0.58}_{-0.09}^{+0.11}\pm 0.13)\%$, $\mathcal{B}(B_s^0\to D_s^{*\pm }{D}_s^{\mp })=({1.76}_{-0.22}^{+0.23}\pm 0.40)\%$, and $\mathcal{B}(B_s^0\to D_s^{*+}{D}_s^{*-})=({1.98}_{-0.31-0.50}^{+0.33+0.52})\%$; the sum is $\mathcal{B}(B_s^0\to D_s^{(*)+}{D}_s^{(*)-})=({4.32}_{-0.39-1.03}^{+0.42+1.04})\%$. Assuming $B_s^0\to D_s^{(*)+}{D}_s^{(*)-}$ saturates decays to $CP$-even final states, the branching fraction constrains the ratio $\Delta {\Gamma }_s/\cos {\varphi }_{12}$, where $\Delta {\Gamma }_s$ is the difference in widths between the two $B_s\mathrm{\text{−}}{\overline{B}}_s$ mass eigenstates, and ${\varphi }_{12}$ is the $CP$-violating phase in $B_s\mathrm{\text{−}}{\overline{B}}_s$ mixing. We also measure for the first time the longitudinal polarization fraction of $B_s^0\to D_s^{*+}{D}_s^{*-}$; the result is ${0.06}_{-0.17}^{+0.18}\pm 0.03$.

We employ the gauge/gravity duality to study the jet quenching of light probes traversing a static yet anisotropic strongly coupled $\mathcal{N}=4$ super Yang-Mills plasma. We compute the stopping distance of an image jet induced by a massless source field, which is characterized by a massless particle falling along the null geodesic in the WKB approximation, in an anisotropic dual geometry introduced by Mateos and Trancancelli. At mid and large anisotropic regimes, the stopping distances of a probe traveling in the anisotropic plasma along various orientations are suppressed compared to those in an isotropic plasma, especially along the longitudinal direction at equal temperature. However, when fixing the entropy density, the anisotropic values of stopping distances near the transverse directions slightly surpass the isotropic values. In general, the jet quenching of light probes is increased by the anisotropic effect in a strongly coupled and equilibrium plasma.

In the standard model, the electroweak $Z$ string can end on a Nambu monopole, whose mass is calculated to be 689 GeV from the current precise experimental data assuming the new particle with mass 125 GeV to be the Higgs boson. We study an extension of the standard model with additional singlet and triplet Higgs fields in the framework of $\mathcal{N}=1$ supersymmetric field theory by using a $D$-brane configuration in type IIA string theory. We construct a $D$-brane configuration describing the electroweak symmetry breaking, and find a single $D2$-brane configuration describing a $Z$ string and a Nambu monopole attached by a $Z$ string in the standard model without an adjoint Higgs field. We further find a single $D2$-brane configuration describing a composite of a ’t Hooft-Polyakov monopole and a Nambu monopole attached by a $Z$ string in an extended standard model with an adjoint Higgs field. We compute the binding energy of the ’t Hooft-Polyakov and Nambu monopoles by solving a minimal surface area of a $D2$-brane.

We compute the scalar gravitational radiation from a binary pulsar system in the simplest model that exhibits the Vainshtein mechanism. The mechanism is successful in screening the effect from scalar fields conformally coupled to matter, although gravitational radiation is less suppressed relative to its general relativity predictions than static fifth forces effects within the pulsar system. This is due to a combination of two effects: firstly, the existence of monopole and dipole radiation; secondly the Vainshtein suppression comes from the hierarchy of scales between the inverse frequency scale and the Vainshtein radius, rather than the orbital radius of the pulsar system. Extensions of these results will have direct relevance to infrared modifications of gravity, such as massive gravity theories, which are known to exhibit a Vainshtein mechanism. Generalization to Galileon models with higher-order interactions are likely to provide stronger constraints.

In investigating the relationship between vorticity and gyroscopic precession, we calculate the vorticity vector in Godel, Kerr, Lewis, Schwarzschild, and Minkowski metrics and find that the vorticity vector of the specific observers is the angular velocity of the gyroscopic precession. Furthermore, when space-time torsion is included, the vorticity and spin-curvature force change sign. This result is very similar to the behavior of the positive and negative helicities of quantum spin in the Stern-Gerlach force. It implies that the inclusion of torsion will lead to an analogous property of quantum spin even in classical treatment.

We study the zeroth law for Killing horizons in Lanczos-Lovelock gravity. We show that the surface gravity of a general Killing horizon in Lanczos-Lovelock gravity (except for general relativity) may not be constant even when the matter source satisfies the dominant energy condition.

We propose a UV completion of the inverse seesaw scenario using fermion $\mathrm{SU}(2{)}_{\mathrm{L}}$ triplet representations. Within this framework, a variation of the standard thermal leptogenesis is achievable at the $\mathcal{O}(\mathrm{TeV})$ scale, owing to the presence of a viable dark matter candidate. This baryogenesis scenario is ruled out if a triplet fermion is observed at the LHC. The dark matter is given by the lightest neutral component of a complex scalar $\mathrm{SU}(2{)}_{\mathrm{L}}$ triplet, with mass $m_{\mathrm{DM}}$ in the TeV range. The scalar sector, which is enriched in order to account for the small neutrino masses, is treated in detail and shows potentially sizable Higgs boson $h\to \gamma \gamma$ rates together with large $h$ invisible branching ratios.