We study the thermodynamic properties associated with the black hole event horizon and the cosmological horizon for black hole solutions in asymptotically de Sitter spacetimes. We examine thermodynamics of these horizons on the basis of the conserved charges according to Teitelboim’s method. In particular, we have succeeded in deriving the generalized Smarr formula among thermodynamical quantities in a simple and natural way. We then show that cosmological constant must decrease when one takes into account the quantum effect. These observations have been obtained if and only if the cosmological constant plays the role of a thermodynamical state variable. We also touch upon the relation between inflation of our universe and a phase transition of black holes.

We discuss the cosmological evolution of the inflationary gravitational wave background in the Randall-Sundrum single-brane model. In braneworld cosmology, in which the three-dimensional spacelike hypersurface that we live in is embedded in five-dimensional anti–de-Sitter (${\mathrm{AdS}}_5$) spacetime, the evolution of gravitational wave (GW) modes is affected by the nonstandard expansion of the universe and the excitation of the Kaluza-Klein modes. These are significant in the high-energy regime of the universe. We numerically evaluate these two effects by solving the evolution equation for GWs propagating through the ${\mathrm{AdS}}_5$ spacetime. Using a plausible initial condition from inflation, we find that the excitation of Kaluza-Klein modes can be characterized by a simple scaling relation above the critical frequency $f_{\mathrm{crit}}$ determined from the length scale of the fifth dimension $\ell$. The remarkable point is that this relation generally holds as long as the matter content of the universe is described by the perfect fluid with the equation of state $p=w\rho$ for $0\le w\le 1$. The resultant scaling relation is translated into the energy spectrum of the inflationary gravitational wave background as ${\Omega }_{\mathrm{GW}}\propto f^{(3w-1)/(3w+2)}$ for $f>f_{\mathrm{crit}}$. This indicates that in the radiation dominant case ($w=1/3$), the two high-energy effects accidentally compensate each other and the spectrum becomes almost the same as the one predicted in the four-dimensional theory, i.e., ${\Omega }_{\mathrm{GW}}\propto f^0$.

We calculate the general solutions for a warm inflationary scenario with weak dissipation, reviewing the dissipative dynamics of the two-fluid system, and calculate the bispectrum of the gravitational field fluctuations generated in the case where dissipation of the vacuum potential during inflation is the mechanism for structure formation, but is the subdominant effect in the dynamics of the scalar field during slow-roll. The bispectrum is nonzero because of the self-interaction of the scalar field. We compare the predictions with both those of standard, or “supercooled“, inflationary models, and warm inflation models with strong dissipation and consider the detectability of these levels of non-Gaussianity in the bispectrum of the cosmic microwave background. We find that the levels of non-Gaussianity for warm and supercooled inflation are an order of magnitude different.

The spectrum of small perturbations about oscillating bounce solutions recently discussed in the literature is investigated. Our study supports quite intuitive and expected result: the bounce with $N$ nodes has exactly $N$ homogeneous negative modes. Existence of more than one negative modes makes obscure the relation of these oscillating bounce solutions to the false vacuum decay processes.

We study inflation arising from the motion of a Bogomol’nyi-Prasad-Sommerfield D3-brane in the background of a stack of $k$ parallel D5-branes. There are two scalar fields in this setup: (i) the radion field $R$, a real scalar field, and (ii) a complex tachyonic scalar field $\chi$ living on the world volume of the open string stretched between the D3 and D5 branes. We find that inflation is realized by the potential of the radion field, which satisfies observational constraints coming from the cosmic microwave background. After the radion becomes of the order of the string length scale $l_s$, the dynamics is governed by the potential of the complex scalar field. Since this field has a standard kinematic term, reheating can be successfully realized by the mechanism of tachyonic preheating with spontaneous symmetry breaking.

We study the primordial gravitational wave background produced in models of single-field inflation. Using the inflationary flow approach, we investigate the amplitude of gravitational wave spectrum, ${\omega }_{\mathrm{gw}}$, in the frequency range 1 mHz–1 Hz pertinent to future space-based laser interferometers. For models that satisfy the current observational constraint on the tensor-to-scalar ratio, $r\lesssim 0.36$, we derive a strict upper bound of ${\omega }_{\mathrm{gw}}\lesssim 1.6\times {10}^{-15}$ independent of the form of the inflationary potential. Applying, in addition, the observational constraints on the spectral index $n_s$ and its running, ${\omega }_{\mathrm{gw}}$ is expected to be considerably lower than this bound unless the shape of the potential is finely tuned. We contrast our numerical results with those based on simple power-law extrapolation of the tensor power spectrum from cosmic microwave background (CMB) scales. In addition to single-field inflation, we summarize a number of other possible cosmological sources of primordial gravitational waves and assess what might be learned from direct detection experiments such as LISA, Big Bang Observer and beyond.

We study the critical behavior at nonzero temperature phase transitions of an effective Hamiltonian derived from lattice QCD in the strong-coupling expansion. Following studies of related quantum spin systems that have a similar Hamiltonian, we show that, for large $N_c$ and fixed $g^2{N}_c$, mean-field scaling is not expected, and that the critical region has a finite width at $N_c=\infty$. A different behavior rises for $N_f\to \infty$ and fixed $N_c$ and $g^2/N_f$, which we study in two spatial dimensions and for $N_c=1$. We find that the width of the critical region is suppressed by $1/N_f^p$ with $p=1/2$, and argue that a generalization to $N_c>1$ and to three dimensions will change this only in detail (e.g. the value of $p>0$), but not in principle. We conclude by stating under what conditions this suppression is expected, and remark on possible realizations of this phenomenon in lattice gauge theories in the continuum.

We examine the possibility of detecting signals of split supersymmetry in the loop-induced decay $h\to \gamma \gamma$ of the Higgs boson at the Large Hadron Collider, where charginos, as surviving light fermions of the supersymmetric spectrum, can contribute in the loop. We perform a detailed study of uncertainties in various parameters involved in the analysis, and thus the net uncertainty in the standard model prediction of the rate. After a thorough scan of the parameter space, taking all constraints into account, we conclude that it will be very difficult to infer about split supersymmetry from Higgs signals alone.

Interactions among the standard model gauge bosons and scalar fields in the framework of the $\mathrm{SU}(3{)}_C\otimes \mathrm{SU}(3{)}_L\otimes \mathrm{U}(1{)}_X$ gauge model with minimal (economical) Higgs content are presented. From these couplings, all scalar fields including the neutral scalar $h$ and the Goldstone bosons can be identified and their couplings with the usual gauge bosons such as the photon, the charged $W^{\pm }$, and the neutral $Z$, without any additional conditions, are recovered. In the effective approximation, the full content of the scalar sector can be recognized. The $CP$-odd part of the Goldstone associated with the neutral non-Hermitian bilepton gauge boson $G_{X^0}$ is decoupled, while its $CP$-even counterpart has the mixing in the same way in the gauge boson sector. Masses of the new neutral Higgs boson $H_1^0$ and the neutral non-Hermitian bilepton $X^0$ are dependent on a coefficient of Higgs self-coupling (${\lambda }_1$). Similarly, masses of the singly charged Higgs boson $H_2^{\pm }$ and of the charged bilepton $Y^{\pm }$ are proportional through a coefficient of Higgs self-interaction (${\lambda }_4$). The hadronic cross section for production of this Higgs boson at the CERN LHC in the effective vector boson approximation is calculated. Numerical evaluation shows that the cross section can exceed 260 fb.

Independent experimental constraints on the initial condition assumed in hydrodynamics to predict collective flow in $\mathrm{Au}+\mathrm{Au}$ at 200 AGeV are essential to strengthen the case for the “perfect fluid” property of deconfined quark-gluon matter. We propose a 3D jet tomographic test of possible novel initial surface geometries predicted by a color glass condensate model of initial conditions. We show that high $p_T$ and rapidity, $\eta$, differential directed flow $v_1(p_T>6,|\eta |>1)$ is sensitive to the generic rapidity twist of the bulk low $p_T$ matter in the reaction plane and can differentiate between conventional diffuse Glauber surfaces and sharper surfaces possible in some parametrizations of the color glass condensate.

We perform a systematic analysis of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrices which arise when one assigns the three generations of leptons to the $2\oplus 1$ representation of a horizontal $S{U}_H(2)$ symmetry. This idea was explored previously by Kuchimanchi and Mohapatra. However, we assume (i) the neutrino mass matrix results from leptonic couplings to $S{U}_L(2)$ triplet scalar fields and (ii) hierarchies exist among lepton mass matrix elements which result from couplings to scalar fields with different $S{U}_H(2)$ charges. Of the 16 candidate PMNS matrices which result it is found that only one is both predictive and possesses a leading order structure compatible with experimental data. The relevant neutrino mass matrix displays the symmetry $L_e-L_{\mu }-L_{\tau }$ to leading order and we explore the perturbations required to produce a realistic lepton spectrum. The effective mass in neutrinoless double beta decay is required to lie in the range $⟨m⟩/({10}^{-2}\mathrm{eV})\in [0.7,2.5]$, which is just below current experimental bounds. $U_{e3}$ is nonzero but not uniquely determined.

We present the final report from a series of precision measurements of the muon anomalous magnetic moment, $a_{\mu }=(g-2)/2$. The details of the experimental method, apparatus, data taking, and analysis are summarized. Data obtained at Brookhaven National Laboratory, using nearly equal samples of positive and negative muons, were used to deduce $a_{\mu }(\mathrm{\text{Expt}})=11659208.0(5.4)(3.3)\times {10}^{-10}$, where the statistical and systematic uncertainties are given, respectively. The combined uncertainty of 0.54 ppm represents a 14-fold improvement compared to previous measurements at CERN. The standard model value for $a_{\mu }$ includes contributions from virtual QED, weak, and hadronic processes. While the QED processes account for most of the anomaly, the largest theoretical uncertainty, $\approx 0.55\mathrm{ppm}$, is associated with first-order hadronic vacuum polarization. Present standard model evaluations, based on $e^{+}{e}^{-}$ hadronic cross sections, lie 2.2–2.7 standard deviations below the experimental result.

We develop the representation of local bulk fields in anti-de Sitter (AdS) space by nonlocal operators on the boundary, working in the semiclassical limit and using ${\mathrm{AdS}}_2$ as our main example. In global coordinates we show that the boundary operator has support only at points which are spacelike separated from the bulk point. We construct boundary operators that represent local bulk operators inserted behind the horizon of the Poincaré patch and inside the Rindler horizon of a two-dimensional black hole. We show that these operators respect bulk locality and comment on the generalization of our construction to higher dimensional AdS black holes.

Dark energy cosmology is considered in a modified Gauss-Bonnet (GB) model of gravity where an arbitrary function of the GB invariant, $f(G)$, is added to the general relativity action. We show that a theory of this kind is endowed with a quite rich cosmological structure: it may naturally lead to an effective cosmological constant, quintessence, or phantom cosmic acceleration, with a possibility for the transition from deceleration to acceleration. It is demonstrated in the paper that this theory is perfectly viable, since it is compliant with the solar system constraints. Specific properties of $f(G)$ gravity in a de Sitter (dS) universe, such as dS and SdS solutions, their entropy, and its explicit one-loop quantization are studied. The issue of a possible solution of the hierarchy problem in modified gravities is also addressed.

We explore in detail a dilatonic scalar-tensor theory of gravity inspired by large extra dimensions, where a radion field from compact extra dimensions gives rise to quintessence in our 4-dimensional world. We show that the model can give rise to other types of cosmologies as well, some more akin to $k$-essence and possibly variants of phantom dark energy. In our model the field (or radius) stabilization arises from quantum corrections to the effective 4D Ricci scalar. We then show that various constraints nearly determine the model parameters, and give an example of a quintessence-type cosmology consistent with observations. We show that the upcoming SNAP-experiment would easily distinguish the present model from a constant $\Lambda$ model with an equal amount of dark energy, but that the SNAP-data alone will not be able distinguish it from a $\Lambda$ model with about 5% less dark energy.

We show that an interaction between dark matter and dark energy generically results in an effective dark-energy equation of state of $w<-1$. This arises because the interaction alters the redshift dependence of the matter density. An observer who fits the data treating the dark matter as noninteracting will infer an effective dark-energy fluid with $w<-1$. We argue that the model is consistent with all current observations, the tightest constraint coming from estimates of the matter density at different redshifts. Comparing the luminosity and angular-diameter distance relations with $\Lambda \mathrm{CDM}$ and phantom models, we find that the three models are degenerate within current uncertainties but likely distinguishable by the next generation of dark-energy experiments.

We present an effective field theory approach to resum the large double logarithms originated from soft-gluon radiations at small final-state hadron invariant masses in Higgs and vector boson $({\gamma }^{*},W,Z)$ production at hadron colliders. The approach is conceptually simple, independent of details of an effective field theory formulation, and valid to all orders in subleading logarithms. As an example, we show the result of summing the next-to-next-to-next-to leading logarithms is identical to that of the standard pQCD factorization method.

We propose a flavor model where both $CP$ and flavor symmetries are broken at the supersymmetric level. The model is an effective SU(5) theory based on a U(2) horizontal symmetry. The minimum of the supersymmetric scalar potential can be exactly solved to yield a realistic pattern of charged fermion masses. The Higgs sector contains a symmetric, an antisymmetric and two vector fields, plus their U(2) conjugates. These Higgs fields are the only fields strictly required to break the flavor and $CP$ symmetries and generate masses for all charged fermions including the up-quark. The model predicts the existence of an absolute minimum in the space of $CP$-phases. The value $\alpha \simeq \pi /2$ is predicted in a particular limit of the parameter space of the model.

The semileptonic process, $B\to \pi l\nu$, is studied via full QCD lattice simulations. We use unquenched gauge configurations generated by the MILC Collaboration. These include the effect of vacuum polarization from three quark flavors: the $s$ quark and two very light flavors ($u/d$) of variable mass allowing extrapolations to the physical chiral limit. We employ nonrelativistic QCD to simulate the $b$ quark and a highly improved staggered quark action for the light sea and valence quarks. We calculate the form factors $f_{+}(q^2)$ and $f_0(q^2)$ in the chiral limit for the range $16{\mathrm{GeV}}^2\le q^2<q_{\max }^2$ and obtain ${\int }_{16{\mathrm{GeV}}^2}^{q_{\max }^2}[d\Gamma /d{q}^2]d{q}^2/|V_{ub}{|}^2=1.46(35){\mathrm{ps}}^{-1}$. Combining this with a preliminary average by the Heavy Flavor Averaging Group (HFAG’05) of recent branching fraction data for exclusive $B$ semileptonic decays from the BABAR, Belle and CLEO Collaborations leads to $|V_{ub}|=4.22(30)(51)\times {10}^{-3}$.