Density response and collective modes of semi-holographic non-Fermi liquids

Semi-holographic models of non-Fermi liquids have been shown to have generically stable generalised quasi-particles on the Fermi surface. Although these excitations are broad and exhibit particle-hole asymmetry, they were argued to be stable from interactions at the Fermi surface. In this work, we use this observation to compute the density response and collective behaviour in these systems. Compared to the Fermi liquid case, we find that the boundaries of the particle-hole continuum are blurred by incoherent contributions. However, there is a region inside this continuum, that we call inner core, within which salient features of the Fermi liquid case are preserved. A particularly striking prediction of our work is that these systems support a plasmonic collective excitation which is well-defined at large momenta, has an approximately linear dispersion relation and is located in the low-energy tail of the particle-hole continuum. Furthermore, the dynamic screening potential shows deep attractive regions as a function of the distance at higher frequencies which might lead to long-lived pair formation depending on the behaviour of the pair susceptibility. We also find that Friedel oscillations are present in these systems but are highly suppressed.Comment: 45 pages; 24 figures; published versio

Time evolution of a toy semiholographic glasma

We extend our previous study of a toy model for coupling classical Yang-Mills equations for describing overoccupied gluons at the saturation scale with a strongly coupled infrared sector modeled by AdS/CFT. Including propagating modes in the bulk we find that the Yang-Mills sector loses its initial energy to a growing black hole in the gravity dual such that there is a conserved energy-momentum tensor for the total system while entropy grows monotonically. This involves a numerical AdS simulation with a backreacted boundary source far from equilibrium.Comment: 17 pages, 7 figures, v2: minor changes in section 3 and acknowledgement

Saturation of the Quantum Null Energy Condition in Far-From-Equilibrium Systems

The Quantum Null Energy Condition (QNEC) is a new local energy condition that a general Quantum Field Theory (QFT) is believed to satisfy, relating the classical null energy condition (NEC) to the second functional derivative of the entanglement entropy in the corresponding null direction. We present the first series of explicit computations of QNEC in a strongly coupled QFT, using holography. We consider the vacuum, thermal equilibrium, a homogeneous far-from-equilibrium quench as well as a colliding system that violates NEC. For vacuum and the thermal phase QNEC is always weaker than NEC. While for the homogeneous quench QNEC is satisfied with a finite gap, we find the interesting result that the colliding system can saturate QNEC, depending on the null direction.Comment: 5 pages, 5 figure

Impact of large-mass constraints on the properties of neutron stars

The maximum mass of a nonrotating neutron star, $M_{\rm TOV}$, plays a very important role in deciphering the structure and composition of neutron stars and in revealing the equation of state (EOS) of nuclear matter. Although with a large-error bar, the recent mass estimate for the black-widow binary pulsar PSR J0952-0607, i.e. $M=2.35\pm0.17~M_\odot$, provides the strongest lower bound on $M_{\rm TOV}$ and suggests that neutron stars with very large masses can in principle be observed. Adopting an agnostic modelling of the EOS, we study the impact that large masses have on the neutron-star properties. In particular, we show that assuming $M_{\rm TOV}\gtrsim 2.35\,M_\odot$ constrains tightly the behaviour of the pressure as a function of the energy density and moves the lower bounds for the stellar radii to values that are significantly larger than those constrained by the NICER measurements, rendering the latter ineffective in constraining the EOS. We also provide updated analytic expressions for the lower bound on the binary tidal deformability in terms of the chirp mass and show how larger bounds on $M_{\rm TOV}$ lead to tighter constraints for this quantity. In addition, we point out a novel quasi-universal relation for the pressure profile inside neutron stars that is only weakly dependent from the EOS and the maximum-mass constraint. Finally, we study how the sound speed and the conformal anomaly are distributed inside neutron stars and show how these quantities depend on the imposed maximum-mass constraints.Comment: 6 pages, 4 figures, 1 appendi

An Approach to Reduce Commissioning and Ramp-up time for Multi-variant Production in Automated Production Facilities

A key requirement for future production facilities is to perform new production processes in a flexible and adaptive way with available and known resources. In this context, a comprehensive description (ontology) of involved components has a high significance. If certain technological aspects are missing during a production process, the production control should respond in a dynamic, versatile and adaptive (agile) manner to the overall value network. The possibility to describe the requirements of products for the necessary processes in the same namespace like the requirements of the necessary processes for the resources is a prerequisite to enable this behavior. Afterwards the different requirements will be placed in relation to the respective requirements. The aim is to define the necessary processes for the production based on the description of the product and the known resources in an agile way. Due to this a framework for a comprehensive description of automated production facilities, products and processes is described in this paper. The idea is that based on this framework a production facility can change the produced products without dedicated commissioning and ramp-up phases

Conversion of ileo-pouch anal anastomosis to continent ileostomy: strategic surgical considerations and outcome

Aim: The aim was to evaluate surgical strategies for conversion of failed ileo-pouch anal anastomosis (IPAA) to continent ileostomy (CI), taking morbidity and overall outcome into account. The hypothesis was that complex conversions are equivalent to the primary construction of a CI at the time of proctocolectomy. Method: This was a retrospective analysis of IPAA conversions acknowledging the underlying disease (inflammatory bowel disease [IBD] and non-IBD) and extent of pouch reconstruction (PR): type 1 (without PR), type 2 (partial PR), and type 3 (complete PR). Results: Twenty-six patients (IBD, n = 16; non-IBD, n = 10) were converted (type 1, n = 13; type 2, n = 7; and type 3, n = 6).12/26 patients (46.2%) presented postoperative complications directly related to the conversion with scarification of two pouches. In a mean follow-up time of 7.5 ± 6.6 years, 5/24 patients required revisional surgery. Of these, three required pouch excision. The cumulative probability of reoperation at the end of the second year increased to 21.7% and remained constant thereafter until the maximum follow-up time of 26 years. The total pouch loss rate was 19.2% (5/26), of which all occurred in the first 3 years. No statistically significant differences were found between the conversion types, complications or pouch survival. For all parameters, IBD patients performed slightly unfavourably. Due to the overall small number of respective patients, a differentiated investigation of IBD was not performed. Conclusion: Complex conversion procedures (types 1 and 2) deliver comparable longterm results to new constructions (type 3), thereby limiting the loss of small bowel. IBD compromises outcome versus non-IBD

Exploring nonlocal observables in shock wave collisions

We study the time evolution of 2-point functions and entanglement entropy in strongly anisotropic, inhomogeneous and time-dependent N=4 super Yang-Mills theory in the large N and large 't Hooft coupling limit using AdS/CFT. On the gravity side this amounts to calculating the length of geodesics and area of extremal surfaces in the dynamical background of two colliding gravitational shockwaves, which we do numerically. We discriminate between three classes of initial conditions corresponding to wide, intermediate and narrow shocks, and show that they exhibit different phenomenology with respect to the nonlocal observables that we determine. Our results permit to use (holographic) entanglement entropy as an order parameter to distinguish between the two phases of the cross-over from the transparency to the full-stopping scenario in dynamical Yang-Mills plasma formation, which is frequently used as a toy model for heavy ion collisions. The time evolution of entanglement entropy allows to discern four regimes: highly efficient initial growth of entanglement, linear growth, (post) collisional drama and late time (polynomial) fall off. Surprisingly, we found that 2-point functions can be sensitive to the geometry inside the black hole apparent horizon, while we did not find such cases for the entanglement entropy.Comment: 28 pp, 9 figs; v2: updated references, changed color bars in Figure 2 and Figure

On the Sound Speed in Neutron Stars

Determining the sound speed $c_s$ in compact stars is an important open question with numerous implications on the behaviour of matter at large densities and hence on gravitational-wave emission from neutron stars. To this scope, we construct more than $10^7$ equations of state (EOSs) with continuous sound speed and build more than $10^8$ nonrotating stellar models consistent not only with nuclear theory and perturbative QCD, but also with astronomical observations. In this way, we find that EOSs with sub-conformal sound speeds, i.e. with $c^2_s < 1/3$ within the stars, are possible in principle but very unlikely in practice, being only $0.03\%$ of our sample. Hence, it is natural to expect that $c^2_s > 1/3$ somewhere in the stellar interior. Using our large sample, we obtain estimates at $95\%$ credibility of neutron-star radii for representative stars with $1.4$ and $2.0$ solar masses, $R_{1.4}=12.42^{+0.52}_{-0.99}\,{\rm km}$, $R_{2.0}=12.12^{+1.11}_{-1.23}\,{\rm km}$, and for the binary tidal deformability of the GW170817 event, $\tilde\Lambda_{1.186}=485^{+225}_{-211}$. Interestingly, our lower-bounds on the radii are in very good agreement with the prediction derived from very different arguments, namely, the threshold mass. Finally, we provide simple analytic expressions to determine the minimum and maximum values of $\tilde\Lambda$ as a function of the chirp mass.Comment: 7 pages + Supplemental Material, 5 figures, comments welcom