The trace of the stress-energy tensor of the cosmological fluid, proportional to the Ricci scalar curvature in general relativity, is determined on cosmic scales for times ranging from the inflationary epoch to the present day in the expanding Universe. The post-inflationary epoch and the thermal history of the relativistic fluid, in particular the QCD transition from asymptotic freedom to confinement and the electroweak phase transition, leave significant imprints on the scalar curvature. These imprints can be of either sign and are orders of magnitude larger than the values that would be obtained by naively extrapolating the pressureless matter of the present epoch back into the radiation-dominated epoch.

We discuss the possibility of having multiple Kaluza-Klein dark matter candidates which arise naturally in generic type-IIB string theory compactification scenarios. These dark matter candidates reside in various throats of the Calabi-Yau manifold. In principle, they can come with a varied range of masses in four dimensions depending upon the hierarchical warping of the throats. We show that consistency with cosmological bounds and four-dimensional effective theory description imposes strong constraints on the parameter space and the geometry of the throats. With a rather model-independent approach, we find that the mass scales allowed for the Kaluza-Klein dark matter particles in various throats can vary between 0.1 eV and 10 TeV, depending upon the throat geometry. Thus, there could be simultaneously more than one kind of cold (and possibly warm and hot) dark matter components residing in the Universe. This multiple dark matter scenario could weaken the bound on a conventional supersymmetric dark matter candidate and could also account for extra relativistic degrees of freedom in our Universe.

The primordial non-Gaussianity parameters $f_{\mathrm{NL}}$ and ${\tau }_{\mathrm{NL}}$ may be scale dependent. We investigate the capability of future measurements of the CMB $\mu$ distortion, which is very sensitive to small scales, and of the large-scale halo bias to test the running of local non-Gaussianity. We show that, for an experiment such as PIXIE, a measurement of the $\mu$-temperature correlation can pin down the spectral indices $n_{f_{\mathrm{NL}}}$ and $n_{{\tau }_{\mathrm{NL}}}$ to values of the order of 0.3 if $f_{\mathrm{NL}}=20$ and ${\tau }_{\mathrm{NL}}=5000$. A similar value can be achieved with an all-sky survey extending to redshift $z\sim 1$. In the particular case in which the two spectral indices are equal, as predicted in models where the cosmological perturbations are generated by a single field other than the inflaton, the $1\sigma$ error on the scale dependence of the nonlinearity parameters goes down to 0.2.

Recently, a lot of effort has been put into describing the thermalization of the quark-gluon plasma using the gauge/gravity duality. In this context, we here present a full numerical solution of the early far-from-equilibrium formation of the plasma, which is expanding radially in the transverse plane and is boost invariant along the collision axis. This can model the early stage of a head-on relativistic heavy ion collision. The resulting momentum distribution quickly reaches local equilibrium, after which it can be evolved using ordinary hydrodynamics. We comment on general implications for these hydrodynamic simulations, both for central and noncentral collisions, and including fluctuations in the initial state.

The “exotic” mesons $X(3872)$, $X(3915)$, $X(3930)$ and $X(3940)$, have been searched for in their radiative production in the $586{\mathrm{pb}}^{-1}$ $e^{+}{e}^{-}$ annihilation data taken with the CLEO-c detector at the $\psi (4160)$ resonance, and their decay in the two modes, $X\to {\pi }^{+}{\pi }^{-}J/\psi$ and $X\to \gamma J/\psi$, with $J/\psi \to {\mu }^{+}{\mu }^{-}$. No evidence for any of the four mesons is found. Upper limits for the product branching fractions, ${\mathcal{B}}_1(\psi (4160)\to \gamma X)\times {\mathcal{B}}_2(X\to {\pi }^{+}{\pi }^{-}J/\psi ,\gamma J/\psi )$ have been determined. The limits at 90% confidence level range from $0.7\times {10}^{-4}$ to $1.8\times {10}^{-4}$.

The interplay of dilatonic effects in dilaton cosmology and stochastic quantum space-time defects within the framework of string/brane cosmologies is examined. The Boltzmann equation describes the physics of thermal dark-matter-relic abundances in the presence of rolling dilatons. These dilatons affect the coupling of stringy matter to $D$-particle defects, which are generic in string theory. This coupling leads to an additional source term in the Boltzmann equation. The techniques of asymptotic matching and boundary-layer theory, which were recently applied by two of the authors (Bender and Sarkar) to a Boltzmann equation, are used here to find the detailed asymptotic relic abundances for all ranges of the expectation value of the dilaton field. The phenomenological implications for the search for supersymmetric dark matter in current colliders, such as the LHC, are discussed.

Excited state spectra are calculated using lattice QCD for baryons that can be formed from $u$, $d$ and $s$ quarks, namely the $N$, $\Delta$, $\Lambda$, $\Sigma$, $\Xi$ and $\Omega$ families of baryons. Baryonic operators are constructed from continuum operators that transform as irreducible representations of $SU(3{)}_F$ symmetry for flavor, $SU(4)$ symmetry for Dirac spins of quarks and $O(3)$ symmetry for orbital angular momenta. Covariant derivatives are used to realize orbital angular momenta. Using the operators, we calculate matrices of correlation functions in order to extract excited states. The resulting lattice spectra have bands of baryonic states with well-defined total spins up to $J=\frac{7}{2}$. Each state can be assigned a dominant flavor symmetry and the counting of states of each flavor and spin reflects $SU(6)\times O(3)$ symmetry for the lowest negative-parity and positive-parity bands. States with strong hybrid content are identified through the dominance of chromomagnetic operators.

In this work we investigate the inclusive and exclusive photoproduction of dileptons, which is relevant for the physics programme to be studied in the proposed electron-proton collider, the LHeC. In the inclusive case, the process is sensitive to the parton distribution functions in the photon, whereas the exclusive channel is connected to the small-$x$ QCD dynamics. For the latter, we investigate the role played by saturation physics at a very high energy scenario. The estimates for production cross sections and the number of events are presented.

The doubly heavy baryon ${\Xi }_{Q{Q}^{\prime }}$ ($Q^{(\prime )}=b$ or $c$) is different from the ordinary baryons. The production of the doubly heavy baryon can provide valuable insight on how the colored $(Q{Q}^{\prime })$ diquark can be transformed into the color-singlet baryon. We study the doubly heavy baryon production through the $e^{+}{e}^{-}$ annihilation channel, $e^{+}+e^{-}\to \gamma /Z^0\to {\Xi }_{Q{Q}^{\prime }}+\overline{Q}+{\overline{Q}}^{\prime }$, within the nonrelativistic QCD framework. We calculate the baryon transverse momentum and the rapidity distributions for all these channels. Typical transverse momentum and rapidity cuts are adopted to show the properties of these distributions in detail. At a $e^{+}{e}^{-}$ collider that runs around the $Z^0$-boson mass with a high luminosity up to $\mathcal{L}\simeq {10}^{34–36}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, in comparison to the Belle and BABAR experiments, it is found that sizable ${\Xi }_{cc}$, ${\Xi }_{bc}$ and ${\Xi }_{bb}$ events can be produced even after performing reasonable baryon transverse momentum and rapidity cuts.

The phenomenology of an unstable particle, including searches and exclusion limits at the LHC, depends significantly on its lineshape. When the width of the resonance is large with respect to its mass, off-shell effects become relevant and the very same definition of width becomes nontrivial. Taking a heavy Higgs boson as an example, we propose a new formulation to describe the lineshape via an effective field theory approach. Our method leads to amplitudes that are gauge invariant, respect unitarity, and can appropriately describe the lineshape of broad resonances. The application of the method to the following relevant processes for the LHC phenomenology have been considered: gluon fusion, vector boson scattering, and $t\overline{t}$ production via weak boson fusion.

We report the determination of the Cabibbo-Kobayashi-Maskawa $CP$-violating angle $\gamma$ through the combination of various measurements involving $B^{\pm }\to D{K}^{\pm }$, $B^{\pm }\to D^{*}{K}^{\pm }$, and $B^{\pm }\to D{K}^{*\pm }$ decays performed by the BABAR experiment at the PEP-II $e^{+}{e}^{-}$ collider at SLAC National Accelerator Laboratory. Using up to 474 million $B\overline{B}$ pairs, we obtain $\gamma =({69}_{-16}^{+17})°$ modulo 180°. The total uncertainty is dominated by the statistical component, with the experimental and amplitude-model systematic uncertainties amounting to $\pm 4°$. The corresponding two-standard-deviation region is $41°<\gamma <102°$. This result is inconsistent with $\gamma =0$ with a significance of 5.9 standard deviations.

We explore the classical production of solitons in the easy axis $O(3)$ model in $1+1$ dimensions, for a wide range of initial conditions that correspond to the scattering of small breathers. We characterize the fractal nature of the region in parameter space that leads to soliton production and find certain trends in the data. We identify a tension in the initial conditions required for soliton production—low velocity incoming breathers are more likely to produce solitons, while high velocity incoming breathers provide momentum to the final solitons and enable them to separate. We find new “counter-spinning” initial conditions that can alleviate some of this tension.

General features of information transfer between quantum subsystems, via unitary evolution, are investigated, with applications to the problem of information transfer from a black hole to its surroundings. A particularly direct form of quantum information transfer is “subsystem transfer,” which can be characterized by the saturation of a subadditivity inequality. We also describe more general unitary quantum information transfer, and categorize different models for black hole evolution. Evolution that only creates paired excitations inside/outside the black hole is shown not to extract information, but information-transferring models exist both in the “saturating” and “nonsaturating” category. The former more closely capture thermodynamic behavior; the latter generically have an enhanced energy flux, beyond that of Hawking.

We present a theorem which allows one to recognize and classify the asymptotic behavior and causal structure of McVittie metrics for different choices of scale factor, establishing whether a black hole or a pair black-white hole appears in the appropriate limit. Incidentally, the theorem also solves an apparent contradiction present in the literature over the causal structure analysis of the McVittie solution. Although the classification we present is not fully complete, we argue that this result covers most if not all physically relevant scenarios.

The nonthermal production of dark matter can provide a large free-streaming length, under which the density fluctuations would be suppressed severely. We explore the nonlinear evolution of cosmological structures in the dark energy dominated model with nonthermal dark matter (NTDM). With the help of -body simulations, we study the nonlinear matter power spectrum, the halo mass function, and the halo density profiles. It is demonstrated that NTDM produces a far lesser number of the subgalactic structures than that of the conventional cold dark matter (CDM). We also find that the density profiles of the low-mass halos in the NTDM model are flat, in contrast to the cuspy cores predicted by the CDM model. The -body simulations show that the inconsistent predictions of the standard model on the galactic and subgalactic scales may be accounted for by the nonthermal mechanism for the production of dark matter.

The most likely spin assignments of the recently discovered 126 GeV resonance are spin 0 or 2. In order to distinguish between the two, we construct an effective Lagrangian model that comprises interactions of a spin-2 electroweak singlet or triplet state with the Standard Model gauge bosons. Within this model, cross sections and differential distributions are calculated and implemented within the Monte Carlo program Vbfnlo, which simulates vector-boson-fusion processes at hadron colliders at next-to-leading order QCD accuracy. We study the phenomenology of spin-2 resonances produced in vector-boson-fusion processes at the LHC. Specifically, we consider light Higgs-like spin-2 resonances decaying into two photons and show how angular distributions allow us to distinguish between a Standard Model Higgs and a spin-2 resonance. We also investigate the characteristics of heavy spin-2 resonances that decay into two weak gauge bosons, leading to a four-lepton final state.

The recently observed increase of direct $CP$ asymmetry in charm meson nonleptonic decays is difficult to explain within the standard model. If this effect is induced by new physics, this might be investigated in other charm processes. We propose to investigate new $CP$-violating effects in rare decays $D\to P{\ell }^{+}{\ell }^{-}$, which arise due to the interference of the resonant part of the long-distance contribution and the new physics affected short-distance contribution. Performing a model-independent analysis, we identify as appropriate observables the differential direct $CP$ asymmetry and partial decay width $CP$ asymmetry. We find that in the most promising decays $D^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$ and $D_s^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ the “peak-symmetric” and “peak-antisymmetric” $CP$ asymmetries are strongly phase dependent and can be of the order 1% and 10%, respectively.

We study cold nuclear matter based on the holographic gauge theory, where baryons are introduced as the instantons in the probe $D8/\overline{\mathrm{D}8}$ branes according to the Sakai-Sugimoto model. Within a dilute gas approximation of instantons, we search for the stable states via the variational method and fix the instanton size. We find the first- order phase transition from the vacuum to the nuclear matter phase as we increase the chemical potential. At the critical chemical potential, we could see a jump in the baryon density from zero to a finite definite value. While the size of the baryon in the nuclear matter is rather small compared to the nucleus near the transition point, where the charge density is also small, it increases with the baryon density. Those behaviors obtained here are discussed by relating them to the force between baryons.

We develop new more powerful techniques, based on an almost closed form for the lattice worldsheet propagator, for analyzing planar open string worldsheets defined on a lightcone lattice. We show that results obtained in earlier work are easily reproduced with far more precision. In particular, consistency checks that required numerical analysis in the earlier work can now be confirmed exactly.

We investigate in detail the vector contributions to the Lagrangian of ${\Lambda }_3$ massive gravity in the decoupling limit, the less explored sector of this theory, with the main aim to study the stability of maximally symmetric self-accelerating solutions. Around self-accelerating configurations, vector degrees of freedom become strongly coupled since their kinetic terms vanish; their dynamics is controlled by contributions to the Lagrangian that arise at higher orders in perturbations. Even in the decoupling limit, the vector Lagrangian contains an infinite number of terms. We develop a systematic method to determine in a covariant way the vector Lagrangian at each order in perturbations, fully manifesting the symmetries of the system. We show that, around self-accelerating solutions, the structure of higher order $p$-form Galileons arise, avoiding the emergence of a sixth ghost Boulware-Deser mode. However, a careful analysis of the corresponding Hamiltonian shows that there are directions along which the Hamiltonian is unbounded from below, signaling an instability that can be interpreted as one of the available fifth modes behaving as a ghost. Hence, we conclude that self-accelerating configurations in the decoupling limit of ${\Lambda }_3$ massive gravity are generically unstable.