Using an on shell gauge invariant formulation of relativistic dynamics I study the interaction vertices for a massive spin $5/2$ Dirac field propagating in (anti–)de Sitter [(A)dS] space of dimension greater than or equal to four. The gravitational interaction vertex for the massive spin $5/2$ field and all cubic vertices for the massive spin $5/2$ field and massless spin 2 field with two and three derivatives are obtained. In dimension greater than four, I demonstrate that the gravitational vertex of the massive spin $5/2$ field involves, in addition to the standard minimal gravitational vertex, contributions with two and three derivatives. I find that for the massive spin $5/2$ and massless spin 2 fields one can build two higher-derivative vertices with two and three derivatives. Limits of massless and partial massless spin $5/2$ fields in (A)dS space and limits of massive and massless spin $5/2$ fields in flat space are discussed.

Theoretical differences in the growth of structure offer the possibility that we might distinguish between modified gravity theories of dark energy and $\Lambda \mathrm{CDM}$. A significant impediment to applying current and prospective large scale galaxy and weak lensing surveys to this problem is that, while the mildly nonlinear regime is important, there is a lack of numerical simulations of nonlinear growth in modified gravity theories. A major question exists as to whether existing analytical fits, created using simulations of standard gravity, can be confidently applied. In this paper we address this, presenting results of N-body simulations of a variety of models where gravity is altered including the Dvali, Gabadadze, and Porrati model. We consider modifications that alter the Poisson equation and also consider the presence of anisotropic shear stress that alters how particles respond to the gravitational potential gradient. We establish how well analytical fits of the matter power spectrum by Peacock and Dodds and Smith et al. are able to predict the nonlinear growth found in the simulations from $z=50$ up to today, and also consider implications for the weak lensing convergence power spectrum. We find that the analytical fits provide good agreement with the simulations, being within $1\sigma$ of the simulation results for cases with and without anisotropic stress and for scale-dependent and independent modifications of the Poisson equation. No strong preference for either analytical fit is found.

The issue concerning the existence of exact black hole solutions in the presence of a nonvanishing cosmological constant and scalar fields is reconsidered. With regard to this, in investigating no-hair theorem violations, exact solutions of gravity having as a source an interacting and conformally coupled scalar field are revisited in arbitrary dimensional nonasymptotically flat space-times. New and known hairy black hole solutions are discussed. The thermodynamical properties associated with these solutions are investigated and the invariance of the black hole entropy with respect to different conformal frames is proved. The issue of the positivity of the entropy is discussed and resolved for the case of black holes immersed in de Sitter space.

The minimal flavor violation hypothesis (MFV) is extended to the $R$-parity violating minimal supersymmetric standard model, supplemented with a simple seesaw mechanism. The requirement of MFV is shown to suppress lepton- and baryon-number violating couplings sufficiently to pass all experimental bounds, in particular, those for proton decay, and is thus a viable alternative to $R$ parity. The phenomenological consequences for flavor-changing neutral currents, lepton flavor violation, and colliders are briefly discussed. Typically, MFV predicts sizable baryon-number violation in some characteristic channels, like single stop resonant production.

Higgs boson productions at the LHC will serve as a sensitive probe of various little Higgs models. In this work we comparatively study two littlest Higgs models with different $T$-parity constructions through examining their effects in three production processes of the Higgs boson at the LHC, namely, the productions of a single Higgs, a Higgs-pair, as well as a Higgs boson associated with a pair of top and antitop quarks. The two models are characterized by predicting a top partner with, respectively, even and odd $T$-parity, which cancels the Higgs mass quadratic divergence caused by the top quark. We find that both models can alter the standard model cross sections sizably and their corrections also differ significantly. Therefore, the Higgs boson productions at the LHC might shed some light on these two models or even distinguish them.

The hadronic charmless $B$ decays into a scalar meson and a vector meson are studied within the framework of QCD factorization. The main results are: (i) The decay rates for the $f_0(980)K^{*-}$ and $f_0(980){\overline{K}}^{*0}$ modes depend on the $f_0-\sigma$ mixing angle $\theta$. (ii) If the $a_0(980)$ is a $q\overline{q}$ bound state, the predicted branching ratios for the color-allowed channels $a_0^{+}{\rho }^{-}$ and $a_0^0{\rho }^{-}$ will be very large, of order $28\times {10}^{-6}$ and $21\times {10}^{-6}$, respectively. (iii) For the $a_0(1450)$ channels, the color-allowed modes $a_0^{+}(1450){\rho }^{-}$ and $a_0^0(1450){\rho }^{-}$ are found to have branching ratios of order $20\times {10}^{-6}$ and $30\times {10}^{-6}$, respectively. A measurement of them at the predicted level will favor the $q\overline{q}$ structure for the $a_0(1450)$. (iv) Contrary to the naive expectation that $\Gamma (B^{-}\to a_0^0{\rho }^{-})\sim \frac{1}{2}\Gamma ({\overline{B}}^0\to a_0^{+}{\rho }^{-})$, we found that this naive relation is violated especially for $a_0=a_0(1450)$ due to additional contributions to the $a_0^0{\rho }^{-}$ mode from the $a_0^0$ emission. (v) The decays $B\to K_0^{*}(1430)\rho$ are expected to have rates substantially larger than that of $B\to K_0^{*}(1430)\pi$ owing to the constructive (destructive) interference between the $a_4$ and $a_6$ penguin terms in the former (latter). Experimentally, it is thus important to check if the $B\to K_0^{*}\rho$ modes are enhanced relative to the corresponding $K_0^{*}\pi$ channels.

We survey 129 lepton number violating effective operators, consistent with the minimal standard model gauge group and particle content, of mass dimension up to and including 11. Upon requiring that each one radiatively generates the observed neutrino masses, we extract an associated characteristic cutoff energy scale which we use to calculate other observable manifestations of these operators for a number of current and future experimental probes, concentrating on lepton number violating phenomena. These include searches for neutrinoless double-beta decay and rare meson, lepton, and gauge boson decays. We also consider searches at hadron/lepton collider facilities in anticipation of the CERN LHC and the future ILC. We find that some operators are already disfavored by current data, while more are ripe to be probed by next-generation experiments. We also find that our current understanding of lepton mixing disfavors a subset of higher dimensional operators. While neutrinoless double-beta decay is the most promising signature of lepton number violation for the majority of operators, a handful is best probed by other means. We argue that a combination of constraints from various independent experimental sources will help to pinpoint the “correct” model of neutrino mass, or at least aid in narrowing down the set of possibilities.

We present a search for the decay $B^{+}\to {\tau }^{+}\nu$ using $383\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$ Factory. We select a sample of events with one completely reconstructed tag $B$ in a hadronic decay mode ($B^{-}\to D^{(*)0}{X}^{-}$), and examine the rest of the event to search for a $B^{+}\to {\tau }^{+}\nu$ decay. We identify the $\tau$ lepton in the following modes: ${\tau }^{+}\to e^{+}\nu \overline{\nu }$, ${\tau }^{+}\to {\mu }^{+}\nu \overline{\nu }$, ${\tau }^{+}\to {\pi }^{+}\overline{\nu }$, and ${\tau }^{+}\to {\pi }^{+}{\pi }^0\overline{\nu }$. We find a $2.2\sigma$ excess in data and measure a branching fraction of $\mathcal{B}(B^{+}\to {\tau }^{+}\nu )=({1.8}_{-0.8}^{+0.9}(\mathrm{stat}.)\pm 0.4(\mathrm{bkg}.\mathrm{syst}.)\pm 0.2(\mathrm{other}\mathrm{syst}.))\times {10}^{-4}$. We calculate the product of the $B$ meson decay constant $f_B$ and $|V_{ub}|$ to be $f_B·|V_{ub}|=({10.1}_{-2.5}^{+2.3}(\mathrm{stat}.{)}_{-1.5}^{+1.2}(\mathrm{syst}.))\times {10}^{-4}\mathrm{GeV}$.

Recently, the Banados-Teitelboim-Zanelli (BTZ) black hole in the presence of the gravitational Chern-Simons term has been studied, and it is found that the usual thermodynamic quantities, like the black hole mass, angular momentum, and entropy, are modified. But, for large values of the gravitational Chern-Simons coupling where the modification terms dominate the original terms some exotic behaviors occur, like the roles of the mass and angular momentum are interchanged and the entropy depends more on the inner horizon area than the outer one. A basic physical problem of this system is that the form of entropy does not guarantee the second law of thermodynamics, in contrast to the Bekenstein-Hawking entropy. Moreover, this entropy does not agree with the statistical entropy, in contrast to a good agreement for small values of the gravitational Chern-Simons coupling. Here I find that there is another entropy formula where the usual Bekenstein-Hawking form dominates the inner-horizon term again, as in the small gravitational Chern-Simons coupling case, such that the second law of thermodynamics can be guaranteed. I also find that the new entropy formula agrees with the statistical entropy based on the holographic anomalies for the whole range of the gravitational Chern-Simons coupling. This reproduces, in the limit of a vanishing Einstein-Hilbert term, the recent result about the exotic BTZ black holes, where their masses and angular momenta are completely interchanged and the entropies depend only on the area of the inner horizon. I compare the result of the holographic approach with the classical-symmetry-algebra-based approach, and I find exact agreements even with the higher-derivative corrections of the gravitational Chern-Simons term. This provides a nontrivial check of the AdS/CFT correspondence, in the presence of higher-derivative terms in the gravity action.

Analyzing closed string tachyon condensation will improve our understanding of spacetime in string theory. We study the string spectrum on a Banados-Teitelboim-Zanelli black hole spacetime supported by Neveu-Schwarz-Neveu-Schwarz flux, which provides a calculable example where we would expect to find a quasilocalized tachyon. We find that there is a winding tachyon when the black hole horizon is smaller than the string scale, as expected. However, due to effects of the Neveu-Schwarz-Neveu-Schwarz $B$ field, this tachyon is not localized in the region where the spatial circle is string scale. We also discuss the relation to the Milne orbifold in the limit near the singularity.

A small simplification based on well-motivated approximations is shown to make loop quantum cosmology of the $k=0$ Friedman-Robertson-Walker model (with a massless scalar field) exactly soluble. Analytical methods are then used i) to show that the quantum bounce is generic; ii) to establish that the matter density has an absolute upper bound which, furthermore, equals the critical density that first emerged in numerical simulations and effective equations; iii) to bring out the precise sense in which the Wheeler-DeWitt theory approximates loop quantum cosmology and the sense in which this approximation fails; and iv) to show that discreteness underlying loop quantum cosmology is fundamental. Finally, the model is compared to analogous discussions in the literature and it is pointed out that some of their expectations do not survive a more careful examination. An effort has been made to make the underlying structure transparent also to those who are not familiar with details of loop quantum gravity.

We study the nonlinear evolution of baryon acoustic oscillations in the dark matter power spectrum and the correlation function using renormalized perturbation theory. In a previous paper we showed that renormalized perturbation theory successfully predicts the damping of acoustic oscillations; here we extend our calculation to the enhancement of power due to mode coupling. We show that mode coupling generates additional oscillations that are out of phase with those in the linear spectrum, leading to shifts in the scales of oscillation nodes defined with respect to a smooth spectrum. When Fourier transformed, these out-of-phase oscillations induce percent-level shifts in the acoustic peak of the two-point correlation function. We present predictions for these shifts as a function of redshift; these should be considered as a robust lower limit to the more realistic case that includes, in addition, redshift distortions and galaxy bias. We show that these nonlinear effects occur at very large scales, leading to a breakdown of linear theory at scales much larger than commonly thought. We discuss why virialized halo profiles are not responsible for these effects, which can be understood from basic physics of gravitational instability. Our results are in excellent agreement with numerical simulations, and can be used as a starting point for modeling baryon acoustic oscillations in future observations. To meet this end, we suggest a simple physically motivated model to correct for the shifts caused by mode coupling.

The dominant method of energy loss by a loop of cosmic D-strings in models of warped brane inflation is studied. It is shown that the energy loss via Ramond-Ramond field radiation can dominate by many orders of magnitude over the energy radiation via gravitational wave emission. The ratio of these two energy loss mechanisms depends on the energy scale of inflation, the mass scale of string theory, and whether it is a single-throat or a multithroat inflationary scenario. This can have important consequences for the detection of cosmic superstrings in the near future. It is argued that the bounds from cosmic microwave background anisotropies and big bang nucleosynthesis are the dominant cosmological sources to constrain the physical parameters of the network of cosmic superstrings, whereas the role of the gravitational wave-based experiments may be secondary.

The contribution of cosmological perturbations to the time drift of the cosmological redshift is derived. It is shown that the dominant correction arises from the local acceleration of both the emitter and the observer. The amplitude of this effect is estimated to be of the order of 1% of the drift signal at $z=2–4$, but can easily be lowered down to 0.1% by using many absorption lines and quasars.

The expectation value of the complex phase factor of the fermion determinant is computed to leading order in the $p$ expansion of the chiral Lagrangian. The computation is valid for $\mu <m_{\pi }/2$ and determines the dependence of the sign problem on the volume and on the geometric shape of the volume. In the thermodynamic limit with $L_i\to \infty$ at fixed temperature $1/L_0$, the average phase factor vanishes. In the low temperature limit where $L_i/L_0$ is fixed as $L_i$ becomes large, the average phase factor approaches 1 for $\mu <m_{\pi }/2$. The results for a finite volume compare well with lattice results obtained by Allton et al. After taking appropriate limits, we reproduce previously derived results for the $ϵ$ regime and for one-dimensional QCD. The distribution of the phase itself is also computed.

In this work, we consider the canonical charmonium assignments for $Y(4360)$ and $Y(4660)$. $Y(4660)$ is a good candidate of $5{}^{3}S_1$ $c\overline{c}$ state, the possibility of $Y(4360)$ as a $3{}^{3}D_1$ $c\overline{c}$ state is studied, and the charmonium hybrid interpretation of $Y(4360)$ cannot be excluded completely. We evaluate the $e^{+}{e}^{-}$ leptonic widths, $E1$ transitions, $M1$ transitions and the open flavor strong decays of $Y(4360)$ and $Y(4660)$. Experimental tests for the charmonium assignments are suggested.

We study the consequences of limited recoil sense reconstruction on the number of events required to reject isotropy and detect a WIMP signal using a directional detector. For a constant probability of determining the sense correctly, 3-d readout and zero background, we find that as the probability is decreased from 1.0 to 0.75 the number of events required increases by a factor of a few. As the probability is decreased further the number of events increases sharply, and isotropy can be rejected more easily by discarding the sense information and using axial statistics. This however requires an order of magnitude more events than vectorial data with perfect sense determination. We also consider energy dependent probabilities of correctly measuring the sense. Our main finding is that correctly determining the sense of the abundant, but less anisotropic, low energy recoils is most important.