arXiv subjects

J. J. Blanco-Pillado

Publications and source records attributed to J. J. Blanco-Pillado.

16 recordsLinked to original sources

arXiv2024

Excited Abelian-Higgs vortices: decay rate and radiation emission

The evolution of 1-vortices when their massive bound mode is excited is investigated in detail (both analytically and numerically) in the Abelian-Higgs model for different ranges of the self-coupling constant. The dependence of the spectrum of the 1-vortex fluctuation operator on the model parameter is discussed initially. A perturbative approach is employed to study the radiation emission in both the scalar and the vector channels. Our findings reveal that the oscillating initial configuration of the 1-vortex radiates at a frequency twice that of the internal mode. Through energy conservation considerations, we derive the decay law of the massive mode. Finally, these analytical results are compared with numerical simulations in field theory.

hep-th↗

arXiv2023

Tunneling Potentials to Nothing

The catastrophic decay of a spacetime with compact dimensions, via bubbles of nothing (BoNs), is probably a generic phenomenon. BoNs admit a 4-dimensional description as singular Coleman-de Luccia bounces of the size modulus field, stabilized by some potential $V(ϕ)$. We apply the tunneling potential approach to this 4d description to provide a very simple picture of BoNs. Using it we identify four different types of BoN, corresponding to different classes of higher dimensional theories. We study the quenching of BoN decays and their interplay with standard vacuum decays.

hep-th↗

arXiv2023

Bubbles of Nothing: The Tunneling Potential Approach

Bubbles of nothing (BoNs) describe the decay of spacetimes with compact dimensions and are thus of fundamental importance for many higher dimensional theories proposed beyond the Standard Model. BoNs admit a 4-dimensional description in terms of a singular Coleman-de Luccia (CdL) instanton involving the size modulus field, stabilized by some potential $V(ϕ)$. Using the so-called tunneling potential ($V_t$) approach, we study which types of BoNs are possible and for which potentials $V(ϕ)$ can they be present. We identify four different types of BoN, characterized by different asymptotic behaviours at the BoN core and corresponding to different classes of higher dimensional theories, which we also classify. Combining numerous analytical and numerical examples, we study the interplay of BoN decays with other standard decay channels, identify the possible types of quenching of BoN decays and show how BoNs for flux compactifications can also be described in 4 dimensions by a multifield $V_t$. The use of the $V_t$ approach greatly aids our analyses and offers a very simple picture of BoNs which are treated in the same language as any other standard vacuum decays.

hep-th↗

arXiv2022

Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review

The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.

hep-ph↗

arXiv2021

The form of cosmic string cusps

We classify the possible shapes of cosmic string cusps and how they transform under Lorentz boosts. A generic cusp can be brought into a form in which the motion of the cusp tip lies in the plane of the cusp. The cusp whose motion is perpendicular to this plane, considered by some authors, is a special case and not the generic situation. We redo the calculation of the energy in the region where the string overlaps itself near a cusp, which is the maximum energy that can be released in radiation. We take into account the motion of a generic cusp and the resulting Lorentz contraction of the string core. The result is that the energy scales as $\sqrt {rL}$ instead of the usual value of $r^{1/3} L^{2/3}$, where $r$ is the string radius and $L$ and is the typical length scale of the string. Since $r << L $ for cosmological strings, the radiation is strongly suppressed and could not be observed.

gr-qc↗

arXiv2006

Inflating in a Better Racetrack

We present a new version of our racetrack inflation scenario which, unlike our original proposal, is based on an explicit compactification of type IIB string theory: the Calabi-Yau manifold P^4_[1,1,1,6,9]. The axion-dilaton and all complex structure moduli are stabilized by fluxes. The remaining 2 Kahler moduli are stabilized by a nonperturbative superpotential, which has been explicitly computed. For this model we identify situations for which a linear combination of the axionic parts of the two Kahler moduli acts as an inflaton. As in our previous scenario, inflation begins at a saddle point of the scalar potential and proceeds as an eternal topological inflation. For a certain range of inflationary parameters, we obtain the COBE-normalized spectrum of metric perturbations and an inflationary scale of M = 3 x 10^{14} GeV. We discuss possible changes of parameters of our model and argue that anthropic considerations favor those parameters that lead to a nearly flat spectrum of inflationary perturbations, which in our case is characterized by the spectral index n_s = 0.95.

hep-th↗

arXiv2004

Racetrack Inflation

We develop a model of eternal topological inflation using a racetrack potential within the context of type IIB string theory with KKLT volume stabilization. The inflaton field is the imaginary part of the Kähler structure modulus, which is an axion-like field in the 4D effective field theory. This model does not require moving branes, and in this sense it is simpler than other models of string theory inflation. Contrary to single-exponential models, the structure of the potential in this example allows for the existence of saddle points between two degenerate local minima for which the slow-roll conditions can be satisfied in a particular range of parameter space. We conjecture that this type of inflation should be present in more general realizations of the modular landscape. We also consider `irrational' models having a dense set of minima, and discuss their possible relevance for the cosmological constant problem.

hep-th↗

arXiv2001

Ultra-high-energy cosmic rays from relic topological defects

It is difficult for conventional sources to accelerate cosmic ray particles to the highest energies that have been observed. Topological defects such as monopoles and strings overcome this difficulty, because their natural energy scale is at or above the observed energies. Monopoles connected by strings are a particularly attractive source, because they would cluster in the galactic halo and thus explain the absence of the GZK cutoff. Heavy monopoles connected by light strings could last for the age of the universe as required. Further observations might support this model by detection of the anisotropy due to the halo, or might refute such models if strong clustering of arrival directions or correlations with known astrophysical objects are confirmed. All top-down models must contend with recent claims that the percentage of photons among the cosmic rays is smaller than such models predict.

astro-ph↗

arXiv2001

Dynamics of superconducting strings with chiral currents

We rederive, using an elementary formalism, the general solution to the equations of motion for a superconducting string with a chiral (null) neutral current, earlier obtained by Carter and Peter. We apply this solution to show that the motion of such string loops is strictly periodic and analyze cusp-like behavior and vorton solutions of arbitrary shape. We argue that this solution can be used to approximately describe the dynamics of superconducting strings with small non-chiral currents. We use this description to estimate the electromagnetic radiation power from such strings.

astro-ph↗

arXiv2000

A vorton gun

In about half of all near-cusp events in superconducting cosmic strings with chiral currents (and probably with general currents as well), the string intersects itself near the cusp. Intercommutation causes the conversion of the string near the cusp into a vorton (in the chiral case) with very high Lorentz boost. We demonstrate how to analyze the cusp shape in a Lorentz frame that makes the motion simple, by the use of a 5-dimensional procedure, and analyze the resulting production of vortons.

astro-ph↗

arXiv2000

Electromagnetic radiation from superconducting string cusps

Cusps in superconducting cosmic strings produce strongly beamed electromagnetic radiation. To calculate the energy emitted requires taking into account the effect of the charge carriers on the string motion, which has previously been done only heuristically. Here, we use the known exact solution to the equations of motion for the case where the current is chiral to update previous calculations for the total energy, spectrum and angular distribution in that case. We analyze the dependence of the radiated energy on the cusp parameters, and discuss which types of cusp dominate the total radiation emitted from an ensemble.

astro-ph↗

arXiv2000

High Energy Cosmic Rays from Neutrinos

We discuss recent models in which neutrinos, which are assumed to have mass in the eV range, originate the highest energy cosmic rays by interaction with the enhanced density in the galactic halo of the relic cosmic neutrino background. We make an analytical calculation of the required neutrino fluxes to show that the parameter space for these models is constrained by horizontal air shower searches and by the total number of background neutrinos, so that only models which have fairly unnatural halo sizes and enhanced densities are allowed.

astro-ph↗

arXiv1999

Radiation from cosmic string standing waves

We have simulated large-amplitude standing waves on an Abelian-Higgs cosmic string in classical lattice field theory. The radiation rate falls exponentially with wavelength, as one would expect from the field profile around a gauge string. Our results agree with those of Shellard and Moore, but not those of Vincent, Antunes, and Hindmarsh. The radiation rate falls too rapidly to sustain a scaling solution via direct radiation of particles from string length. There is thus reason to doubt claims of strong constraints on cosmic string theories from cosmic ray observations.

astro-ph↗

arXiv1999

Monopole-antimonopole bound states as a source of ultra-high-energy cosmic rays

The electromagnetic decay and final annihilation of magnetic monopole-antimonopole pairs formed in the early universe has been proposed as a possible mechanism to produce the highest energy cosmic rays. We show that for a monopole abundance saturating the Parker limit, the density of magnetic monopolonium formed is many orders of magnitude less than that required to explain the observed cosmic ray flux. We then propose a different scenario in which the monopoles and antimonopoles are connected by strings formed at a low energy phase transition (~ 100 GeV). The bound states decay by gravitational radiation, with lifetimes comparable with the age of the universe. This mechanism avoids the problems of the standard monopolonium scenario, since the binding of monopoles and antimonopoles is perfectly efficient.

astro-ph↗

arXiv1998

Field theory simulation of Abelian-Higgs cosmic string cusps

We have performed a lattice field theory simulation of cusps in Abelian-Higgs cosmic strings. The results are in accord with the theory that the portion of the strings which overlaps near the cusp is released as radiation. The radius of the string cores which must touch to produce the evaporation is approximately $r = 1$ in natural units. In general, the modifications to the string shape due to the cusp may produce many cusps later in the evolution of a string loop, but these later cusps will be much smaller in magnitude and more closely resemble kinks.

gr-qc↗

arXiv1996

Limits on Topological Defect Neutrino fluxes from Horizontal Air Shower measurements

We obtain the horizontal air shower rate from the (EeV) high energy neutrino flux predicted in some topological defect scenarios as the source for the highest energy cosmic rays. Emphasis is made on the different character of the events depending on the neutrino flavor an type of interaction. We show that the bound for muon poor showers in the $10^5-10^7$ GeV energy range is violated by maximal predictions for superconducting cosmic string neutrino fluxes, we compare it to other neutrino flux limits and we discuss the future of such measurements to further constrain these models.

astro-ph↗