We study some non leptonic and semileptonic decays of the $B_s$ meson into a final scalar meson $f_0(980)$ in the fourth quark generation model. Since the $f_0(980)$ meson is dominantly composed of the ($s\overline{s}$) pair, the mixing-induced $CP$ asymmetry in the decay mode $B_s\to J/\psi f_0(980)$ would a priori give $\sin 2{\beta }_s$, where ${\beta }_s$ is the $B_s-{\overline{B}}_s$ mixing phase. In the standard model this asymmetry is expected to be vanishingly small. We find that in the fourth generation model a large mixing-induced $CP$ asymmetry could be possible for this process. Similarly the branching ratios of the rare semileptonic decays $B_s\to f_0(980)l^{+}{l}^{-}$ and $B_s\to f_0(980)\nu \overline{\nu }$ are found to be enhanced significantly from their corresponding standard model values.

We derive the effective action of the hard large-$x$ valence charges up to fourth order in their density. Such non-Gaussian weight functionals contribute at leading order in $N_c$ to the connected two-gluon production diagrams that determine di-hadron correlations. The corresponding diagrams are not necessarily (highly) suppressed by the density of valence charges since their infrared divergences differ from those obtained in a Gaussian theory. Therefore, it appears prudent to include such higher dimensional operators when determining initial ensembles for nonlinear evolution of higher $n$-point functions of Wilson lines.

Soft-collinear effective theory (SCET) is applied to compute electroweak radiative corrections to Higgs production via gauge boson fusion, $qq\to qqH$. There are several novel features which make this process an interesting application of SCET: The amplitude is proportional to the Higgs vacuum expectation value, and so is not a gauge singlet amplitude. Standard resummation methods require a gauge singlet operator and do not apply here. The SCET analysis requires operators with both collinear and soft external fields, with the Higgs vacuum expectation value being described by an external soft $\varphi$ field. There is a scalar soft-collinear transition operator in the SCET Lagrangian which contributes to the scattering amplitude, and is derived here.

Experimental searches for lepton-flavor-violating coherent muon-to-electron conversion in the field of a nucleus, have been proposed to reach the unprecedented sensitivity of ${10}^{-16}–{10}^{-18}$ per stopped muon. At that level, they probe new interactions at effective-mass scales well beyond 1000 TeV. However, they must contend with background from ordinary bound muon decay. To better understa560nd the background-spectrum shape and rate, we have carried out a detailed analysis of Coulombic-bound-state muon decay, including nuclear recoil. Implications for future experiments are briefly discussed.

We construct a method to supersymmetrize higher kinetic terms and apply it to the baby Skyrme model. We find that there exist $N=1$ supersymmetric extensions for baby Skyrme models with arbitrary potential.

This paper discusses the quantum mechanics of closed-timelike curves (CTCs) and of other potential methods for time travel. We analyze a specific proposal for such quantum time travel, the quantum description of CTCs based on post-selected teleportation (P-CTCs). We compare the theory of P-CTCs to previously proposed quantum theories of time travel: the theory is inequivalent to Deutsch’s theory of CTCs, but it is consistent with path-integral approaches (which are the best suited for analyzing quantum-field theory in curved space-time). We derive the dynamical equations that a chronology-respecting system interacting with a CTC will experience. We discuss the possibility of time travel in the absence of general-relativistic closed-timelike curves, and investigate the implications of P-CTCs for enhancing the power of computation.

We investigate a pointlike massive source in nonlinear $f(R)$ theories in the case of an arbitrary number of spatial dimensions $D\ge 3$. If $D>3$ then extra dimensions undergo toroidal compactification. We consider a weak-field approximation with Minkowski and de Sitter background solutions. In both these cases pointlike massive sources demonstrate good agreement with experimental data only in the case of ordinary three-dimensional ($D=3$) space. We generalize this result to the case of a perfect fluid with dustlike equations of state in the external and internal spaces. This perfect fluid is uniformly smeared over all extra dimensions and enclosed in a three-dimensional sphere. In ordinary three-dimensional ($D=3$) space, our formulas are useful for experimental constraints on parameters of $f(R)$ models.

We present new results on the dynamics and gravitational-wave emission from the collapse of differentially rotating neutron stars. We have considered a number of polytropic stellar models having different values of the dimensionless angular momentum $J/M^2$, where $J$ and $M$ are the asymptotic angular momentum and mass of the star, respectively. For neutron stars with $J/M^2<1$, i.e. “sub-Kerr” models, we were able to find models that are dynamically unstable and that collapse promptly to a rotating black hole. Both the dynamics of the collapse and the consequent emission of gravitational waves resemble those seen for uniformly rotating stars, although with an overall decrease in the efficiency of gravitational-wave emission. For stellar models with $J/M^2>1$, i.e. “supra-Kerr” models, on the other hand, we were not able to find models that are dynamically unstable and all of the computed supra-Kerr models were found to be far from the stability threshold. For these models a gravitational collapse is possible only after a very severe and artificial reduction of the pressure, which then leads to a torus developing nonaxisymmetric instabilities and eventually contracting to a stable axisymmetric stellar configuration. While this does not exclude the possibility that a naked singularity can be produced by the collapse of a differentially rotating star, it also suggests that cosmic censorship is not violated and that generic conditions for a supra-Kerr progenitor do not lead to a naked singularity.

We study gravitational collapse of a spherically symmetric inhomogeneous dust cloud in the Lovelock theory without cosmological constant. We show that the final fate of gravitational collapse in this theory depends on the spacetime dimensions. In odd dimensions the naked singularities formed are found to be massive. In the even dimensions, on the other hand, the naked singularities are found to be massless. We also show that the curvature strength of naked singularity is independent of the spacetime dimensions in odd dimensions. However, it depends on the spacetime dimensions in even dimension.

We consider $f(R,T)$ modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar $R$ and of the trace of the stress-energy tensor $T$. We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Generally, the gravitational field equations depend on the nature of the matter source. The field equations of several particular models, corresponding to some explicit forms of the function $f(R,T)$, are also presented. An important case, which is analyzed in detail, is represented by scalar field models. We write down the action and briefly consider the cosmological implications of the $f(R,T^{\varphi })$ models, where $T^{\varphi }$ is the trace of the stress-energy tensor of a self-interacting scalar field. The equations of motion of the test particles are also obtained from a variational principle. The motion of massive test particles is nongeodesic, and takes place in the presence of an extra-force orthogonal to the four velocity. The Newtonian limit of the equation of motion is further analyzed. Finally, we provide a constraint on the magnitude of the extra acceleration by analyzing the perihelion precession of the planet Mercury in the framework of the present model.

We study the geometry inside the event horizon of perturbed $D$ dimensional Reissner-Nordström–(anti)de Sitter type black holes showing that, similarly to the four dimensional case, mass inflation also occurs for $D>4$. First, using the homogeneous approximation, we show that an increase of the number of spatial dimensions contributes to a steeper variation of the metric coefficients with the areal radius and that the phenomenon is insensitive to the cosmological constant in leading order. Then, using the code reported in [P. P. Avelino, A. J. S. Hamilton, and C. A. R. Herdeiro, Phys. Rev. D 79, 124045 (2009).] adapted to $D$ dimensions, we perform fully nonlinear numerical simulations. We perturb the black hole with a compact pulse adapting the pulse amplitude such that the relative variation of the black hole mass is the same in all dimensions and determine how the black hole interior evolves under the perturbation. We qualitatively confirm that the phenomenon is similar to four dimensions as well as the behavior observed in the homogeneous approximation. We speculate about the formation of black holes inside black holes triggered by mass inflation, and about possible consequences of this scenario.

We study the accretion process in the region of the Preston-Poisson space-time describing a Schwarzschild black hole perturbed by an asymptotically uniform magnetic field and axisymmetric tidal structures. We find that the accretion disk shrinks and the marginally stable orbit shifts toward the black hole with the perturbation. The radiation intensity of the accretion disk increases, while the radius where radiation is maximal remains unchanged. The spectrum is blue-shifted. Finally, the conversion efficiency of accreting mass into radiation is decreased by both the magnetic and the tidal perturbations.

The channeling of the ion recoiling after a collision with a weakly interacting massive particle (WIMP) in direct dark matter crystalline detectors produces a larger scintillation or ionization signal than otherwise expected. Channeling is a directional effect, which depends on the velocity distribution of WIMPs in the dark halo of our Galaxy and could lead to a daily modulation of the signal. Here we compute upper bounds to the expected amplitude of daily modulation due to channeling using channeling fractions that we obtained with analytic models in prior work. After developing the general formalism, we examine the possibility of finding a daily modulation due to channeling in the data already collected by the DAMA/NaI and DAMA/LIBRA experiments. We find that even the largest daily modulation amplitudes (of the order of 10% in some instances) would not be observable for WIMPs in the standard halo in the 13 years of data taken by the DAMA Collaboration. For these to be observable, the DAMA total rate should be $1/40$ of what it is or the total DAMA exposure should be 40 times larger. The daily modulation due to channeling will be difficult to measure in future experiments. We find it could be observed for light WIMPs in solid Ne, assuming no background.

In the case of a large class of static, spherically symmetric black hole solutions in higher order modified gravity models, an expression for the associated energy is proposed and identified with a quantity proportional to the constant of integration, which appears in the explicit solution. The identification is achieved making use of derivation of the first law of black hole thermodynamics from the equations of motion, evaluating independently the entropy via the Wald method and the Hawking temperature via quantum mechanical methods in curved space-times. Several nontrivial examples are discussed, including a new topological higher derivative black hole solution, and the proposal is shown to work in all examples considered.

We consider on-center and off-center observers in an inhomogeneous, spherically symmetric, isocurvature (flat) concentration of dark energy with a typical size of a few Gpc. Such a concentration could be produced e.g. by a recently formed global monopole with core size that approaches the Hubble scale. In this case we would have what may be called “topological quintessence” in analogy with the well-known topological inflation. We show that the minimum comoving radius $r_{0\min }$ of such a dark energy inhomogeneity that is consistent with the Union2 type Ia supernovae data at the $3\sigma$ level is $r_{0\min }\simeq 1.8\mathrm{Gpc}$. As expected, the best-fit fractional dark energy density at the center, ${\Omega }_{X,\mathrm{in}}$, approaches the corresponding $\Lambda \mathrm{CDM}$ value ${\Omega }_{X,\mathrm{in}}=0.73$ for large enough values of the inhomogeneity radius $r_0$ ($r_0>4\mathrm{Gpc}$). Using the Union2 data, we show that the maximum allowed shift $r_{\mathrm{obs}\mathrm{\text{−}}\max }$ of the observer from the center of the inhomogeneity is about $0.7r_0$, which respects the Copernican principle. The model naturally predicts the existence of a preferred axis and alignment of the low CMB multipoles. However, the constraints on $r_{\mathrm{obs}\mathrm{\text{−}}\max }$ coming from the magnitude of the CMB dipole remain a severe challenge to the Copernican principle and lead to $r_{\mathrm{obs}\mathrm{\text{−}}\max }<110\mathrm{Mpc}$, even for an inhomogeneity radius as large as $r_0=7\mathrm{Gpc}$.

There is a standard story about decay in multidimensional flux landscapes: that from any state, the fastest decay is to take a small step, discharging one flux unit at a time; that fluxes with the same coupling constant are interchangeable; and that states with $N$ units of a given flux have the same decay rate as those with -$N$. We show that this standard story is false. The fastest decay is a giant leap that discharges many different fluxes in unison; this decay is mediated by a “minimal” brane that wraps the internal manifold and exhibits behavior not visible in the effective theory. We discuss the implications for the cosmological constant problem.

A conformally invariant hidden sector is considered, with a scalar operator $\mathcal{O}$ of low dimension that couples to the electroweak gauge bosons of the standard model, via terms such as $F^{\mu \nu }{F}_{\mu \nu }\mathcal{O}$. By examining single photon production at LEP, we bound the strength of these interactions. We apply our results, along with those of Delgado and Strassler [A. Delgado and M. J. Strassler, Phys. Rev. D 81, 056003(2010).] and of Caracciolo and Rychkov [F. Caracciolo and S. Rychkov, Phys. Rev. D 81, 085037 (2010).], to improve the bound on $4\gamma$ production through “unparticle self-interactions,” as proposed by Feng et al. [J. L. Feng, A. Rajaraman, and H. Tu, Phys. Rev. D 77, 075007 (2008).]. We find the maximum allowable cross section is of order a few tens of femtobarns at the 14 TeV LHC, and lies well below 1 fb for a wide range of parameters.

The electroweak chiral Lagrangian for the topcolor-assisted technicolor model proposed by K. Lane, which uses nontrivial patterns of techniquark condensation and walking, was investigated in this study. We found that the features of the model are qualitatively similar to those of Lane’s previous natural topcolor-assisted technicolor prototype model, but there is no limit on the upper bound of the $Z^{\prime }$ mass. We discuss the phase structure and possible walking behavior of the model. We obtained the values of all coefficients of the electroweak chiral Lagrangian up to an order of $p^4$. We show that although the walking effect reduces the $S$ parameter to half its original value, it maintains an order of 2. Moreover, a special hypercharge arrangement is needed to achieve further reductions in its value.

We compare the first results on searches for supersymmetry with the Large Hadron Collider (LHC) to the current and near-term performance of experiments sensitive to neutralino dark matter. We limit our study to the particular slices of parameter space of the constrained minimal supersymmetric extension to the standard model where CMS and ATLAS exclusion limits have been presented so far. We show where, on that parameter space, the lightest neutralino possesses a thermal relic abundance matching the value inferred by cosmological observations. We then calculate rates for, and estimate the performance of, experiments sensitive to direct and indirect signals from neutralino dark matter. We argue that this is a unique point in time, where the quest for supersymmetry—at least in one of its practical and simple incarnations—is undergoing a close scrutiny from the LHC and from dark matter searches that is both synergistic and complementary. Should the time of discovery finally unravel, the current performances of the collider program and of direct and indirect dark matter searches are at a conjuncture offering unique opportunities for a breakthrough on the nature of physics beyond the standard model.

We present a focused study of a predictive unified model whose measurable consequences are immediately relevant to early discovery prospects of supersymmetry at the LHC. ATLAS and CMS have released their analysis with $35{\mathrm{pb}}^{-1}$ of data and the model class we discuss is consistent with this data. It is shown that with an increase in luminosity, the LSP dark matter mass and the gluino mass can be inferred from simple observables such as kinematic edges in leptonic channels and peak values in effective mass distributions. Specifically, we consider cases in which the neutralino is of low mass and where the relic density consistent with WMAP observations arises via the exchange of Higgs bosons in unified supergravity models. The magnitudes of the gaugino masses are sharply limited to focused regions of the parameter space, and, in particular, the dark matter mass lies in the range $\sim (50–65)\mathrm{GeV}$ with an upper bound on the gluino mass of 575 GeV, with a typical mass of 450 GeV. We find that all model points in this paradigm are discoverable at the LHC at $\sqrt{s}=7\mathrm{TeV}$. We determine lower bounds on the entire sparticle spectrum in this model based on existing experimental constraints. In addition, we find the spin-independent cross section for neutralino scattering on nucleons to be generally in the range of ${\sigma }_{{\tilde{\chi }}_1^{0}p}^{\mathrm{SI}}={10}^{-46\pm 1}{\mathrm{cm}}^2$ with much higher cross sections also possible. Thus, direct detection experiments such as CDMS and XENON already constrain some of the allowed parameter space of the low mass gaugino models and further data will provide important cross-checks of the model assumptions in the near future.