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Recently, we studied perturbations in the Lemaitre-Tolman-Bondi cosmological model by applying the second-order perturbation theory in the dust Friedmann-LemaTtre-Robertson-Walker universe model. Before this work, the same subject was studied in some papers by analyzing linear perturbations in the Lemaitre-Tolman-Bondi cosmological model under the assumption proposed by Clarkson, Clifton, and February, in which two perturbation variables are negligible. However, it is a nontrivial issue in what situation the Clarkson-Clifton-February assumption is valid. In this paper, we investigate differences between these two approaches. It is shown that, in general, these two approaches are not compatible with each other. That is, in our perturbative procedure, the Clarkson-Clifton-February assumption is not valid at the order of our interest. [ABSTRACT FROM AUTHOR]

If a single-mode nonclassical light is combined with the vacuum on a beam splitter, then the output state is entangled. As proposed in [Phys. Rev. Lett. 94, 173602 (2005)], by measuring this output-state entanglement for a balanced lossless beam splitter, one can quantify the input-state nonclassicality. These measures of nonclassicality (referred to as entanglement potentials) can be based, in principle, on various entanglement measures, leading to the negativity (NP) and concurrence (CP) potentials, and the potential for the relative entropy of entanglement (REEP). We search for the maximal relative nonclassicality, which can be achieved by comparing two entanglement measures for (i) arbitrary two-qubit states and (ii) those which can be generated from a photon-number qubit via a balanced lossless beam splitter, where the qubit basis states are the vacuum and single-photon states. Surprisingly, we find that the maximal relative nonclassicality, measured by the REEP for a given value of the NP, can be increased (if NP < 0.527) by using either a tunable beam splitter or by amplitude damping of the output state of the balanced beam splitter. We also show that the maximal relative nonclassicality, measured by the NP for a given value of the REEP, can be increased by phase damping (dephasing). Note that the entanglement itself is not increased by these losses (since they act locally), but the possible ratios of different measures are affected. Moreover, we show that partially dephased states can be more nonclassical than both pure states and completely dephased states, by comparing the NP for a given value of the REEP. Thus, one can conclude that not all standard entanglement measures can be used as entanglement potentials. Alternatively, one can infer that a single balanced lossless beam splitter is not always transferring the whole nonclassicality of its input state into the entanglement of its output modes. The application of a lossy beam splitter can solve this problem, at least for the cases analyzed in this paper. [ABSTRACT FROM AUTHOR]

Dynamical decoupling protocols are one of the most used tools for efficient quantum error corrections and for reservoir engineering. In this paper we study the effect of dynamical decoupling pulses on the preservation of both quantum and classical correlations, and their influence on the intriguing phenomenon of time-invariant discord. We study two qubits experiencing local dephasing with an Ohmic class spectrum and subject to dynamical decoupling protocols. We investigate the connection between the dynamics of both classical and quantum correlations and the behavior of information flow between system and environment. Finally, we establish a set of necessary conditions for which time-invariant discord can be created using dynamically decoupling techniques. [ABSTRACT FROM AUTHOR]

Composite Higgs models are intriguing scenarios in which the Higgs particle is identified as a pseudo-Nambu-Goldstone boson associated with spontaneous breaking of some global symmetry above the electroweak scale. They would predict new resonances at high-energy scales, some of which can appear at multi-TeV scales. In such a case, analogies with the pion physics in QCD, where a sizable phase shift is predicted in pion-pion scattering processes, might help us to evaluate scales of the resonances. In this paper, we discuss two complementary approaches to investigate the compositeness scale in minimal composite Higgs models. First, we discuss the bound on vector boson scattering from perturbative unitarity, and we evaluate the phase shift of the scattering amplitude, assuming that the same fitting function as one in the case of the pion physics can be applied. We then obtain the relation between possible phase shifts and promising new resonance scales. We also investigate the possibility to measure the phase shift at LHC and the future hadron colliders. Second, we classify deviations in Higgs coupling constants from the standard model predictions in various kinds of the minimal composite Higgs models. We then discuss a possibility to discriminate a specific minimal composite Higgs model from the other models with extended Higgs sectors by utilizing deviation patterns in the Higgs boson couplings by future precision measurements. [ABSTRACT FROM AUTHOR]

The Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach for the investigation of semihard processes is plagued by large next-to-leading corrections, both in the kernel of the universal BFKL Green's function and in the process-dependent impact factors, as well as by large uncertainties in the renormalization scale setting. All that calls for an optimization procedure of the perturbative series. In this respect, one of the most common methods is the Brodsky-Lepage-Mackenzie (BLM) one, which eliminates the renormalization scale ambiguity by absorbing the nonconformal β0 terms into the running coupling. In this paper, we apply the BLM scale setting procedure directly to the amplitudes (cross sections) of several semihard processes. We show that, due to the presence of β0 terms in the next-to-leading expressions for the impact factors, the optimal renormalization scale is not universal but depends both on the energy and on the type of process in question. [ABSTRACT FROM AUTHOR]

This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above 1.5 GeV using the large fiducial mass of the T2K π0 detector. The predominant portion of the ve νℯ flux (~85%) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is 0.89 ± 0.08(stat) ± 0.11 (sys), and with the water targets emptied is 0.90 ± 0.09(stat) ± 0.13 (sys). The ratio obtained for the interactions on water only from an event subtraction method is 0.87 ± 0.33(stat) ± 0.21 (sys). This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors. [ABSTRACT FROM AUTHOR]

This paper investigates the manner in which classical universes are obtained in the no-boundary quantum state. In this context, universes can be characterized as classical [in a Wentzel-Kramers-Brillouin (WKB) sense] when the wavefunction is highly oscillatory, i.e. when the ratio of the change in the amplitude of the wavefunction becomes small compared to the change in the phase. In the presence of a positive or negative exponential potential, the WKB condition is satisfied in proportion to a factor e-(ε-3)N/(ε-1), where ε is the (constant) slow-roll/fast-roll parameter and N designates the number of e-folds. Thus classicality is reached exponentially fast in N, but only when ε < 1 (inflation) or ε > 3 (ekpyrosis). Furthermore, when the potential switches off and the ekpyrotic phase goes over into a phase of kinetic domination, the level of classicality obtained up to that point is preserved. Similar results are obtained in a cyclic potential, where a dark energy plateau is added. Finally, for a potential of the form -ɸn (with n=4,6,8), where the classical solution becomes increasingly kinetic dominated, there is an initial burst of classicalization which then quickly levels off. These results demonstrate that inflation and ekpyrosis, which are the only dynamical mechanisms known for smoothing the universe, share the perhaps even more fundamental property of rendering space and time classical in the first place. [ABSTRACT FROM AUTHOR]

Theories of physics beyond the standard model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs boson to the top quark. With extensions of the standard model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the standard model particles. This results in corrections to the Higgs production and decay rates that can be detected at the LHC provided the top partners are sufficiently light, and the theory correspondingly natural. In this paper we consider three theories that address the little hierarchy problem and involve colorless top partners, specifically the mirror twin Higgs, folded supersymmetry, and the quirky little Higgs. For each model we investigate the current and future bounds on the top partners, and the corresponding limits on naturalness, that can be obtained from the Higgs program at the LHC. We conclude that the LHC will not be able to strongly disfavor naturalness, with mild tuning at the level of about one part in ten remaining allowed even with 3000 fb-1 of data at 14 TeV. [ABSTRACT FROM AUTHOR]

The presence of charged scalars is almost inevitable in most of the beyond standard model scenarios. They are expected to be detected easily if they are there due to their electromagnetic charge. These charged scalars can be produced at the LHC and their decays may lead to interesting signals--multilepton final states, displaced vertices, etc. These charged particles also play crucial roles in low energy rare processes. Thus apart from the collider searches in low energy rare processes their presence can be smelled. Here, we have noted the impact of doubly charged scalars in rare meson decays. As the mesons are lighter these heavy scalars always appear off shell. Due to their off-shell structure the phase space is relatively complicated to deal with. In this paper we have supplemented a general proposal to compute these decays that involve off-shell doubly charged scalars. We have argued that our prescription can be used for any process involving off-shell heavy scalars. Using the prescribed method we have computed two possible meson decays: ... We have also estimated the numerical values of the branching ratios in different channels for different charged mesons. [ABSTRACT FROM AUTHOR]

Cosmology based on large scale peculiar velocity prefers volume weighted velocity statistics. However, measuring the volume weighted velocity statistics from inhomogeneously distributed galaxies (simulation particles/halos) suffers from an inevitable and significant sampling artifact. We study this sampling artifact in the velocity power spectrum measured by the nearest particle velocity assignment method by Zheng et al., [Phys. Rev. D 88, 103510 (2013).]. We derive the analytical expression of leading and higher order terms. We find that the sampling artifact suppresses the z = 0 E-mode velocity power spectrum by ~10% at k = 0.1 h/Mpc, for samples with number density 10-3 (Mpc/h)-3. This suppression becomes larger for larger k and for sparser samples. We argue that this source of systematic errors in peculiar velocity cosmology, albeit severe, can be self-calibrated in the framework of our theoretical modelling. We also work out the sampling artifact in the density-velocity cross power spectrum measurement. A more robust evaluation of related statistics through simulations will be presented in a companion paper by Zheng et al., [Sampling artifact in volume weighted velocity measurement. II. Detection in simulations and comparison with theoretical modelling, arXiv: 1409.6809.]. We also argue that similar sampling artifact exists in other velocity assignment methods and hence must be carefully corrected to avoid systematic bias in peculiar velocity cosmology. [ABSTRACT FROM AUTHOR]

Measuring the volume weighted velocity power spectrum suffers from a severe systematic error due to imperfect sampling of the velocity field from the inhomogeneous distribution of dark matter particles/halos in simulations or galaxies with velocity measurement. This "sampling artifact" depends on both the mean particle number density ñP and the intrinsic large scale structure (LSS) fluctuation in the particle distribution. (1) We report robust detection of this sampling artifact in V-body simulations. It causes ~12% underestimation of the velocity power spectrum at k = 0.1 h/Mpc for samples with ñP = 6 × 10-3 (Mpc/h)-3. This systematic underestimation increases with decreasing hP and increasing k. Its dependence on the intrinsic LSS fluctuations is also robustly detected. (2) All of these findings are expected based upon our theoretical modeling in paper I [P. Zhang, Y. Zheng, and Y. Jing, Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling, arXiv:1405.7125.]. In particular, the leading order theoretical approximation agrees quantitatively well with the simulation result for ñP ≳ 6 × 10-4 (Mpc/h)-3. Furthermore, we provide an ansatz to take high order terms into account. It improves the model accuracy to ≲ 1% at k ≲ 0.1 h/Mpc over 3 orders of magnitude in ñP and over typical LSS clustering from z = 0 to z = 2. (3) The sampling artifact is determined by the deflection D field, which is straightforwardly available in both simulations and data of galaxy velocity. Hence the sampling artifact in the velocity power spectrum measurement can be self-calibrated within our framework. By applying such self-calibration in simulations, it is promising to determine the real large scale velocity bias of 1013M⊚ halos with ~1% accuracy, and that of lower mass halos with better accuracy. (4) In contrast to suppressing the velocity power spectrum at large scale, the sampling artifact causes an overestimation of the velocity dispersion. We prove that a correlation between the signal field (v) and the sampling field (D) is a major cause. This complexity, among other issues, is carefully investigated to further improve understanding of the sampling artifact. [ABSTRACT FROM AUTHOR]

In the Lemaître-Tolman (L-T) models that have nonconstant bang-time function tB(r), light emitted close to those points of the big bang where dtB/dr ≄ 0 is blueshifted at the receiver position. The blueshifted rays are expected to perturb the temperature of the cosmic microwave background radiation along the lines of sight of the present central observer. It is shown here that, in a general L-T model, the tB(r) can be chosen so that the blueshift-generating region is hidden before the recombination time, where the L-T model does not apply. The rest of the paper is devoted to investigating blueshifts in one specific L-T model, called L-T(tB)--the one that duplicates the luminosity distance vs redshift relation of the ACDM model using nonconstant tB(r) alone. The location of the blueshift-generating region in the L-T(tB) spacetime is determined. Profiles of redshift/blueshift along several rays intersecting the past light cone of the present central observer are calculated. The L-T(tB) model matched to Friedmann is considered, and profiles of redshift/blueshift in such a composite model are calculated. The requirement of invisibility of blueshifts makes the L-T(tB) model astrophysically unacceptable if it should apply back to the recombination time, but it does not "rule out" a general L-T model--it only puts limits on dtB/dr. [ABSTRACT FROM AUTHOR]

The fact that closed timelike curves (CTCs) are permitted by general relativity raises the question as to how quantum systems behave when time travel to the past occurs. Research into answering this question by utilizing the quantum circuit formalism has given rise to two theories: Deutschian-CTCs (D-CTCs) and "postselected" CTCs (P-CTCs). In this paper the quantum circuit approach is thoroughly reviewed, and the strengths and shortcomings of D-CTCs and P-CTCs are presented in view of their nonlinearity and time-travel paradoxes. In particular, the "equivalent circuit model"--which aims to make equivalent predictions to D-CTCs, while avoiding some of the difficulties of the original theory--is shown to contain errors. The discussion of D-CTCs and P-CTCs is used to motivate an analysis of the features one might require of a theory of quantum time travel, following which two overlapping classes of alternate theories are identified. One such theory, the theory of "transition probability" CTCs (T-CTCs), is fully developed. The theory of T-CTCs is shown not to have certain undesirable features--such as time-travel paradoxes, the ability to distinguish nonorthogonal states with certainty, and the ability to clone or delete arbitrary pure states--that are present with D-CTCs and P-CTCs. The problems with nonlinear extensions to quantum mechanics are discussed in relation to the interpretation of these theories, and the physical motivations of all three theories are discussed and compared. [ABSTRACT FROM AUTHOR]

The question of whether classically conformal modifications of the standard model are consistent with experimental observations has recently been subject to renewed interest. The method of Gildener and Weinberg provides a natural framework for the study of the effective potential of the resulting multiscalar standard model extensions. This approach relies on the assumption of the ordinary loop hierarchy λs ~ gg² of scalar and gauge couplings. On the other hand, Andreassen et al. recently argued that in the (single-scalar) standard model gauge invariant results require the consistent scaling λs ~ gg4. In the present paper, we contrast these two hierarchy assumptions and illustrate the differences in the phenomenological predictions of minimal conformal extensions of the standard model. [ABSTRACT FROM AUTHOR]

Twist fields were introduced a few decades ago as a quantum counterpart to classical kink configurations and disorder variables in low dimensional field theories. In recent years they received a new incarnation within the framework of geometric entropy and strong coupling limit of four-dimensional scattering amplitudes. In this paper, we study their two-point correlation functions in a free massless scalar theory, namely, twist-twist and twist-antitwist correlators. In spite of the simplicity of the model in question, the properties of the latter are far from being trivial. The problem is reduced, within the formalism of the path integral, to the study of spectral determinants on surfaces with conical points, which are then computed exactly making use of the zeta function regularization. We also provide an insight into twist correlators for a massive complex scalar by means of the Lifshitz-Krein trace formula. [ABSTRACT FROM AUTHOR]

In this paper we study the direct CP asymmetry of the doubly Cabibbo-suppressed decay mode D0→K+π- within standard model and two Higgs doublet model with generic Yukawa structure. In the standard model we derive the corrections to the tree level amplitude, generated from the box and dipenguin diagrams, required for generating the weak CP violating phases. We show that these phases are so tiny leading to a direct CP asymmetry of order 10-9. Regarding the two Higgs doublet model with generic Yukawa structure we derive the Wilson coefficients relevant to D0→K+π-. After taking into account all constraints on the parameter space of the model we show that charged Higgs couplings to quarks can lead to a direct CP asymmetry of order 10-3 which is 6 orders of magnitude larger than the standard model prediction. [ABSTRACT FROM AUTHOR]

In this paper, we construct and study solutions of Einstein's equations in a vacuum with a positive cosmological constant which can be considered as inhomogeneous generalizations of the Nariai cosmological model. Similar to this Nariai spacetime, our solutions are at the borderline between gravitational collapse and de Sitter-like exponential expansion. Our studies focus in particular on the intriguing oscillatory dynamics which we discover. Our investigations are carried out both analytically (using heuristic mode analysis arguments) and numerically (using the numerical infrastructure recently introduced by us). [ABSTRACT FROM AUTHOR]

Nonminimal composite Higgs scenarios can contain exotic Higgs states which, if observed at the Large Hadron Collider, will help to constrain the underlying UV structure of the strong dynamics. Doubly charged Higgs bosons are well-motivated scalar degrees of freedom in this context. Their phenomenology in typical composite scenarios can differ from well-established Higgs triplet extensions of the SM. Related search strategies are not necessarily adapted to such a scenario as a consequence. In this paper we discuss the sensitivity reach to doubly charged Higgs bosons with decays into pairs of same-sign W bosons. While production cross sections are small, we show that significant constraints on H±±→W±W± can be obtained, providing a new opportunity to constrain the potential composite structure of the TeV scale up to mH±±≃800 GeV. [ABSTRACT FROM AUTHOR]