The 1-loop computation of the processes ${\tilde{\chi }}_i^0{\tilde{\chi }}_j^0\to \gamma Z$ has been performed at an arbitrary c.m. energy for any pair of MSSM neutralinos. As an application suitable for dark matter (DM) searches, the neutralino-neutralino annihilation is studied at the limiting case of vanishing relative velocity, describing the present DM distribution in the galactic halo; and at a relative velocity of about 0.5, determining the neutralino relic density contributions. The most useful situation is obviously for $i=j=1$, but the case of nonidentical neutralinos may also be useful in some corners of the parameter space. Our results are contained in the FORTRAN code PLATONdmgZ, applying to any set of real MSSM parameters. Numerical results are also presented for a sample of 6 MSSM models, describing the various possible neutralino properties. A comparison with other existing works is also made.

The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving $R_{\mathrm{up}/\mathrm{down}}^{\mathrm{data}}/R_{\mathrm{up}/\mathrm{down}}^{\mathrm{MC}}={0.62}_{-0.14}^{+0.19}(\mathrm{stat}.)\pm 0.02(\mathrm{sys}.)$. An extended maximum likelihood analysis of the observed $L/E$ distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ interactions are separated. The ratio of ${\overline{\nu }}_{\mu }$ to ${\nu }_{\mu }$ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving $R_{{\overline{\nu }}_{\mu }/{\nu }_{\mu }}^{\mathrm{data}}/R_{{\overline{\nu }}_{\mu }/{\nu }_{\mu }}^{\mathrm{MC}}={0.96}_{-0.27}^{+0.38}(\mathrm{stat}.)\pm 0.15(\mathrm{sys}.)$, where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$.

The two-photon width of ${\chi }_{c2}({}^{3}P_2)$ state of charmonium has been measured using $14.4{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ data taken at $\sqrt{s}=9.46–11.30\mathrm{GeV}$ with the CLEO III detector. The $\gamma \gamma$-fusion reaction studied is $e^{+}{e}^{-}\to e^{+}{e}^{-}\gamma \gamma$, $\gamma \gamma \to {\chi }_{c2}\to \gamma J/\psi \to \gamma e^{+}{e}^{-}({\mu }^{+}{\mu }^{-})$. We measure ${\Gamma }_{\gamma \gamma }({\chi }_{c2})\mathcal{B}({\chi }_{c2}\to \gamma J/\psi )\mathcal{B}(J/\psi \to e^{+}{e}^{-}+{\mu }^{+}{\mu }^{-})=13.2\pm 1.4(\mathrm{stat})\pm 1.1(\mathrm{syst})\mathrm{eV}$, and obtain ${\Gamma }_{\gamma \gamma }({\chi }_{c2})=559\pm 57(\mathrm{stat})\pm 48(\mathrm{syst})\pm 36(\mathrm{br})\mathrm{eV}$. This result is in excellent agreement with the result of $\gamma \gamma$-fusion measurement by Belle and is consistent with that of the $\overline{p}p\to {\chi }_{c2}\to \gamma \gamma$ measurement, when they are both reevaluated using the recent CLEO result for the radiative decay ${\chi }_{c2}\to \gamma J/\psi$.

In this report, we study within the context of general relativity with one extra dimension compactified either on a circle or an orbifold, how radion fluctuations interact with metric fluctuations in the three noncompact directions. The background is nonsingular and can either describe an extra dimension on its way to stabilization, or immediately before and after a series of nonsingular bounces. We find that the metric fluctuations transfer undisturbed through the bounces or through the transients of the stabilization epoch. Our background is obtained by considering the effects of a gas of massless string modes in the context of a consistent “massless background” (or low energy effective theory) limit of string theory. We discuss applications to various approaches to early universe cosmology, including the ekpyrotic/cyclic universe scenario and string gas cosmology.

The potential $V(x)=-x^4$, which is unbounded below on the real line, can give rise to a well-posed bound state problem when $x$ is taken on a contour in the lower-half complex plane. It is then $PT$-symmetric rather than Hermitian. Nonetheless it has been shown numerically to have a real spectrum, and a proof of reality, involving the correspondence between ordinary differential equations and integrable systems, was subsequently constructed for the general class of potentials $-(ix{)}^N$. For such Hamiltonians the natural $PT$ metric is not positive definite, but a dynamically-defined positive-definite metric can be defined, depending on an operator $Q$. Further, with the help of this operator an equivalent Hermitian Hamiltonian $h$ can be constructed. This programme has been carried out exactly for a few soluble models, and the first few terms of a perturbative expansion have been found for the potential $m^2{x}^2+ig{x}^3$. However, until now, the $-x^4$ potential has proved intractable. In the present paper we give explicit, closed form expressions for $Q$ and $h$, which are made possible by a particular parametrization of the contour in the complex plane on which the problem is defined. This constitutes an explicit proof of the reality of the spectrum. The resulting equivalent Hamiltonian has a potential with a positive quartic term together with a linear term.

Suppose the Universe comes into existence (as classical spacetime) already with an empty spherically symmetric macroscopic wormhole present in it. Classically the wormhole would evolve into a part of the Schwarzschild space and thus would not allow any signal to traverse it. I consider semiclassical corrections to that picture and build a model of an evaporating wormhole. The model is based on the assumption that the vacuum polarization and its backreaction on the geometry of the wormhole are weak. The lack of information about the era preceding the emergence of the wormhole results in appearance of three parameters which—along with the initial mass—determine the evolution of the wormhole. For some values of these parameters the wormhole turns out to be long-lived enough to be traversed and to transform into a time machine.

I show that massive-particle dynamics can be simulated by a weak, external perturbation on a potential flow in an ideal fluid. The perturbation defining a particle is dictated in a small (spherical) region that is otherwise free to roam in the fluid. Here I take it as an external potential that couples to the fluid density or as a rigid distribution of sources with vanishing total outflux. The effective Lagrangian for such particles is shown to be of the form $m{c}^2\ell (U^2/c^2)$, where $\overrightarrow{U}$ is the velocity of the particle relative to the fluid and $c$ the speed of sound. This can serve as a model for emergent relativistic inertia à la Mach’s principle with $m$ playing the role of inertial mass, and also of analog gravity where $m$ is also the passive gravitational mass. The mass $m$ depends on the particle type and intrinsic structure (and on position if the background density is not constant), while $\ell$ is universal: For $D$-dimensional particles $\ell \propto F(1,1/2;D/2;U^2/c^2)$ ($F$ is the hypergeometric function). These particles have the following interesting dynamics: Particles fall in the same way in the analog gravitational field mimicked by the flow, independent of their internal structure, thus satisfying the weak equivalence principle. For $D\le 5$ they all have a relativistic limit with the acquired energy and momentum diverging as $U\to c$. For $D\le 7$ the null geodesics of the standard acoustic metric solve our equation of motion. Interestingly, for $D=4$ the dynamics is very nearly Lorentzian: $\ell \propto -m{c}^2{\gamma }^{-1}\lambda (\gamma )$ (up to a constant), with $\lambda =(1+{\gamma }^{-1}{)}^{-1}$ varying between $1/2$ and 1 ($\gamma$ is the “Lorentz factor” for the particle velocity relative to the fluid). The particles can be said to follow the geodesics of a generalized acoustic metric of a Finslerian type that shares the null geodesics with the standard acoustic metric. In vortex geometries, the ergosphere is automatically the static limit. As in the real world, in “black hole” geometries circular orbits do not exist below a certain radius that occurs outside the horizon. There is a natural definition of antiparticles, and I describe a mock particle vacuum in whose context one can discuss, e.g., particle Hawking radiation near event horizons.

In this paper we investigate the trace anomaly in a space-time where single events are delocalized as a consequence of short distance quantum coordinate fluctuations. We obtain a modified form of heat kernel asymptotic expansion which does not suffer from short distance divergences. Calculation of the trace anomaly is performed using an IR regulator in order to circumvent the absence of UV infinities. The explicit form of the trace anomaly is presented and the corresponding $2D$ Polyakov effective action and energy-momentum tensor are obtained. The vacuum expectation value of the energy-momentum tensor in the Boulware, Hartle-Hawking and Unruh vacua is explicitly calculated in a $rt$ section of a recently found, noncommutative inspired, Schwarzschild-like solution of the Einstein equations. The standard short distance divergences in the vacuum expectation values are regularized in agreement with the absence of UV infinities removed by quantum coordinate fluctuations.

The consequences of spin-rotation-gravity coupling are worked out for linear gravitational waves. The coupling of helicity of the wave with the rotation of a gravitational-wave antenna is investigated and the resulting modifications in the Doppler effect and aberration are pointed out for incident high-frequency gravitational radiation. Extending these results to the case of a gravitomagnetic field via the gravitational Larmor theorem, the rotation of linear polarization of gravitational radiation propagating in the field of a rotating mass is studied. It is shown that in this case the linear polarization state rotates by twice the Skrotskii angle as a consequence of the spin-2 character of linear gravitational waves.

Positively-curved, oscillatory universes have recently been shown to have important consequences for the preinflationary dynamics of the early universe. In particular, they may allow a self-interacting scalar field to climb up its potential during a very large number of these cycles. The cycles are naturally broken when the potential reaches a critical value and the universe begins to inflate, thereby providing a “graceful entrance” to early universe inflation. We study the dynamics of this behavior within the context of braneworld scenarios which exhibit a bounce from a collapsing phase to an expanding one. The dynamics can be understood by studying a general class of braneworld models that are sourced by a scalar field with a constant potential. Within this context, we determine the conditions a given model must satisfy for a graceful entrance to be possible in principle. We consider the bouncing braneworld model proposed by Shtanov and Sahni and show that it exhibits the features needed to realise a graceful entrance to inflation for a wide region of parameter space.

We consider the question of asymptotic observables in cosmology. We assume that string theory contains a landscape of vacua, and that metastable de Sitter regions can decay to a zero cosmological constant by bubble nucleation. The asymptotic properties of the corresponding bounce solution should be incorporated in a nonperturbative quantum theory of cosmology. A recent proposal for such a framework defines an $S$ matrix between the past and future boundaries of the bounce. We analyze in detail the properties of asymptotic states in this proposal, finding that generic small perturbations of the initial state cause a global crunch. We conclude that late-time amplitudes should be computed directly. This would require a string theory analog of the no-boundary proposal.

We propose a new parametrization of the deceleration parameter to study its time-variation behavior. The advantage of parameterizing the deceleration parameter is that we do not need to assume any underlying theory of gravity. By fitting the model to the 157 gold sample supernova Ia data, we find strong evidence that the Universe is currently accelerating and it accelerated in the past. By fitting the model to the 115 nearby and Supernova Legacy Survey supernova Ia data, the evidence that the Universe is currently accelerating is weak, although there is still a strong evidence that the Universe once accelerated in the past. The results obtained from the 157 gold sample supernova Ia data and those from the 115 supernova Ia data are not directly comparable because the two different data sets measure the luminosity distance up to different redshifts. We then use the Friedmann equation and a dark energy parametrization to discuss the same problem. When we fit the model to the supernova Ia data alone, we find weak evidence that the Universe is accelerating and the current matter density is higher than that measured from other experiments. After we add the Sloan Digital Sky Survey data to constrain the dark energy model, we find that the behavior of the deceleration parameter is almost the same as that obtained from parameterizing the deceleration parameter.

The dynamical effects of the tensor modes of the geometry are investigated in the context of curvature bounces. Since the bouncing behavior implies sharp deviations from a radiation-dominated evolution, significant backreaction effects of relic gravitons may be expected at short wavelengths. After developing a general iterative framework for the calculation of dynamical backreaction effects, explicit analytical and numerical examples are investigated for different parametrizations of the energy-momentum pseudotensor(s) of the produced gravitons. The reported results suggest that dynamical backreaction effects are a necessary ingredient for a consistent description of bouncing models at late times.

We investigate the spatial clustering properties of primordial black holes (PBHs). With minimal assumptions, we show that PBHs created in the radiation era are highly clustered. Using the peaks theory model of bias, we compute the PBH two-point correlation function and power spectrum. For creation from an initially adiabatic power spectrum of perturbations, the PBH power spectrum contains both isocurvature and adiabatic components. The absence of observed isocurvature fluctuations today constrains the mass range in which PBHs may serve as dark matter. We briefly discuss other consequences of PBH clustering.

Great uncertainty surrounds dark energy, both in terms of its physics, and the choice of methods by which the problem should be addressed. Here we quantify the redshift sensitivities offered by different techniques. We focus on the three methods most adept at constraining $w$, namely, supernovae, cosmic shear, and baryon oscillations. For each we provide insight into the family of $w(z)$ models which are permitted for a particular constraint on either $w=w_0$ or $w=w_0+w_a(1-a)$. Our results are in the form of “weight functions”, which describe the fitted model parameters as a weighted average over the true functional form. For example, we find the recent best-fit from the Supernovae Legacy Survey ($w=-1.023$) corresponds to the average value of $w(z)$ over the range $0<z<0.4$. Whilst there is a strong dependence on the choice of priors, each cosmological probe displays distinctive characteristics in their redshift sensitivities. In the case of proposed future surveys, a SNAP-like supernova survey probes a mean redshift of $z\sim 0.3$, with baryon oscillations and cosmic shear at $z\sim 0.6$. If we consider the evolution of $w$, sensitivities shift to slightly higher redshift. Finally, we find that the weight functions may be expressed as a weighted average of the popular “principal components”.

Lattice QCD studies of hadron-hadron interactions are performed by computing the energy levels of the system in a finite box. The shifts in energy levels proportional to inverse powers of the volume are related to scattering parameters in a model independent way. In addition, there are nonuniversal exponentially suppressed corrections that distort this relation. These terms are proportional to $e^{-m_{\pi }L}$ and become relevant as the chiral limit is approached. In this paper we report on a one-loop chiral perturbation theory calculation of the leading exponential corrections in the case of $I=2$ $\pi \pi$ scattering near threshold.

We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process $pp\to W^{\pm }X$ at the BNL Relativistic Heavy Ion Collider (RHIC). At RHIC, polarized protons are available, and spin asymmetries for this process will be used for precise measurements of the up and down quark and antiquark distributions in the proton. The corrections arise near the threshold for the partonic reaction and are associated with soft-gluon emission. We perform the resummation to next-to-leading logarithmic accuracy, for the rapidity-differential cross section. We find that resummation leads to relatively moderate effects on the cross sections and spin asymmetries.

The $B$-meson light-cone wave functions, ${\Psi }_{\pm }(\omega ,z^2)$, are investigated up to the next-to-leading order in Fock state expansion in the heavy-quark limit. In order to know the transverse momentum dependence of the $B$-meson wave functions with 3-particle Fock states’ contributions, we make use of the relations between 2- and 3- particle wave functions derived from the QCD equations of motion and the heavy-quark symmetry, especially two constraints derived from the gauge field equation of motion are employed. Our results show that the use of gluon equation of motion can give a constraint on the transverse momentum dependence $\chi (\omega ,{\mathbf{k}}_{\perp })$ of the $B$-meson wave functions, whose distribution tends to be a hyperbolalike curve under the condition $0<c_1<1$, which is quite different from the Wandzura-Wilczek-(WW)-type wave functions, whose transverse momentum dependence ${\chi }^{\mathrm{WW}}(\omega ,{\mathbf{k}}_{\perp })$ is merely a delta function. Based on the derived results, we propose a simple model for the $B$-meson wave functions with 3-particle Fock states’ contributions.

We pursue the program of the study of the nonforward amplitude in heavy quark effective theory (HQET). We obtain new sum rules involving the elastic subleading form factors ${\chi }_i(w)$ $(i=1,2,3)$ at order $1/m_Q$ that originate from the ${\mathcal{L}}_{kin}$ and ${\mathcal{L}}_{mag}$ perturbations of the Lagrangian. To obtain these sum rules we use two methods. On the one hand we start simply from the definition of these subleading form factors, and on the other hand, we use the operator product expansion. To the sum rules contribute only the same intermediate states $(j^P,J^P)=({\frac{1}{2}}^{-},1^{-}),({\frac{3}{2}}^{-},1^{-})$ that enter in the $1/m_Q^2$ corrections of the axial form factor $h_{A_1}(w)$ at zero recoil. This allows to obtain a lower bound on $-{\delta }_{1/m^2}^{(A_1)}$ in terms of the ${\chi }_i(w)$ and the shape of the elastic IW function $\xi (w)$. We find also lower bounds on the $1/m_Q^2$ correction to the form factors $h_{+}(w)$ and $h_1(w)$ at zero recoil. An important theoretical implication is that ${\chi }_1^{\prime }(1)$, ${\chi }_2(1)$ and ${\chi }_3^{\prime }(1)$ (${\chi }_1(1)={\chi }_3(1)=0$ from Luke theorem) would vanish if the slope and the curvature of $\xi (w)$, ${\rho }^2\ge \frac{3}{4}$, ${\sigma }^2\ge \frac{15}{16}$, would attain their lowest bounds. We discuss possible implications on the precise determination of $|V_{cb}|$.

A shape of the unitary triangle versus a $CP$ violating parameter $\delta$ depends on the phase conventions of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix, because the $CP$ violating parameter $\delta$ cannot directly be observed, so that it is not rephasing-invariant. In order to seek for a clue to the quark mass matrix structure and the origin of the $CP$ violation, the dependence of the unitary triangle shape on the parameter $\delta$ is systematically investigated.