This is a review of particle-theory models of inflation, and of their predictions for the primordial density perturbation that is thought to be the origin of structure in the Universe. It contains mini-reviews of the relevant observational cosmology, of elementary field theory and of supersymmetry, that may be of interest in their own right. The spectral index n(k), specifying the scale dependence of the spectrum of the curvature perturbation, will be a powerful discriminator between models, when it is measured by Planck with accuracy Δn∼0.01. The usual formula for n is derived, as well as its less familiar extension to the case of a multi-component inflaton; in both cases the key ingredient is the separate evolution of causally disconnected regions of the Universe. Primordial gravitational waves will be an even more powerful discriminator if they are observed, since most models of inflation predict that they are completely negligible. We treat in detail the new wave of models, which are firmly rooted in modern particle theory and have supersymmetry as a crucial ingredient. The review is addressed to both astrophysicists and particle physicists, and each section is fairly homogeneous regarding the assumed background knowledge.
Ernesto F. Eiroa, Emilio Rubín de Celis, Claudio Simeone
In this article we study spherical thin-shell wormholes in five-dimensional Einstein–Gauss–Bonnet gravity. We show that configurations supported by non-exotic matter, that is matter satisfying the weak energy condition, are possible at the same time that traversability problems associated with strong radial tides at the throat can be avoided when suitable values of the parameters are adopted. Our construction is performed in such a way that it also allows for the admissible behaviour of the geometry in the whole spacetime.
Abstract The ultimate goal of understanding the structure of matter has spurred a constant search for composite particles, especially high-order correlated entities for nearly all forms of matter, from elementary particles, nuclei, and cold atoms, to condensed matter. So far, composite particles involving two or three constituent particles and their weak-coupling combinations have been experimentally studied, such as the Cooper pairs, excitons, trions, and bi-excitons in condensed matter physics, or diquarks, mesons, and di-mesons in quantum chromodynamics. Although genuine four-particle correlated entities have long been theorized in various materials, alternatively known as quadruplons (Rausch and Potthoff in New J. Phys. 18, 2016), quadrons (Quang et al. in Physica B 602, 2021), or quartets (Jiang et al. in Phys. Rev. B 95, 2017), the only closely related experimental evidence is the tetraquark observation at CERN (LHCb in Nat. Phys. 18, 751–754, 2022). In this article, we present for the first time the experimental evidence for the existence of a four-body entity in condensed matter, the quadruplon, involving two electrons and two holes in a monolayer of Molybdenum Ditelluride. Using the optical pump–probe technique, we discovered a series of new spectral features in addition to those of excitons and trions. Furthermore, we found that all these spectral features could be reproduced theoretically using transitions between the two-body and four-body complexes based on the Bethe–Salpeter equation. Interestingly, we found that the fourth-order irreducible cluster is necessary and sufficient for the new spectral features by using the corresponding cluster expansion technique. Thus, our experimental results combined with theoretical explanation provide strong evidence for the existence of a genuine four-particle entity, the quadruplon. In contrast to a bi-exciton which consists of two weakly interacting excitons, a quadruplon involves tightly bound four-particle entity without the presence of well-defined excitons. Our results could impact the understanding of the structure of materials in a wide range of physical systems and potentially lead to new photonic applications based on quadruplons.
In this work, we employ the nonextensive Nambu–Jona-Lasinio model to analyze the thermodynamic properties of magnetized quark matter. The nonequilibrium state is described in Tsallis distribution by a dimensionless parameter <i>q</i>. We find that within a reasonable temperature range, the system undergoes a crossover transition at the critical chemical potential, which is decreased by the increase of both the temperature and <i>q</i> value. In contrast to the enhanced stability by magnetic field in Boltzmann statistics, it is found that the stability of chiral restored matter in Tsallis statistics would be reduced by an increase of the magnetic field. Conversely, the increase of the <i>q</i> would enhance the stability of quark matter. Finally, we display the different magnetic effects on the stability in the chiral broken and restored regions.
The ATLAS collaboration, G. Aad, E. Aakvaag
et al.
Abstract A search is performed for dark matter particles produced in association with a resonant pair of Higgs bosons using 140 fb −1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. This signature is expected in some extensions of the Standard Model predicting the production of dark matter particles, and is interpreted in terms of a dark Higgs model containing a Z′ mediator in which the dark Higgs boson s decays into a pair of Higgs bosons. The dark Higgs boson is reconstructed through final states with at least three b-tagged jets, produced by the pair of Higgs boson decays, in events with significant missing transverse momentum consistent with the presence of dark matter. The observed data are found to be in good agreement with Standard Model predictions, constraining scenarios with dark Higgs boson masses within the range of 250 to 400 GeV and Z′ mediators up to 2.3 TeV.
Nuclear and particle physics. Atomic energy. Radioactivity
Stuart Marongwe, Moletlanyi Tshipa, Christian Corda
We present a Bayesian statistical analysis to evaluate the Nexus Paradigm (NP) of quantum gravity, using horizon-scale observations of supermassive black holes (SMBHs) Sagittarius A* (Sgr A*) and M87* from the Event Horizon Telescope (EHT). The NP predicts angular diameters for the dark depression, emission ring, and base diameter, which we compare to EHT measurements. Employing Gaussian likelihoods and priors informed by mass-to-distance ratio uncertainties, we compute the posterior distribution for the angular scale parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>θ</mi></mrow><mrow><mi>g</mi></mrow></msub></mrow></semantics></math></inline-formula>, achieving a combined <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>χ</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≈</mo><mn>0.0062</mn></mrow></semantics></math></inline-formula> (four degrees of freedom) corresponding to a 4.37<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mi>σ</mi></mrow></semantics></math></inline-formula> (99.9972%) confidence level. Individual features show deviations <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo><</mo><mn>0.1</mn><mo> </mo><mi>σ</mi></mrow></semantics></math></inline-formula> supporting the NP’s claim of 99th percentile agreement. Compared to General Relativity (GR), which predicts a shadow diameter inconsistent with the observed dark depression (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>χ</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≈</mo><mn>168</mn><mo>,</mo><mo> </mo><mo>~</mo><mn>12.97</mn><mo> </mo><mi>σ</mi></mrow></semantics></math></inline-formula>) the NP is favored with a Bayes factor of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>~</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>36</mn></mrow></msup></mrow></semantics></math></inline-formula>. These results validate the NP’s predictions and highlight its potential as a quantum gravity framework, though refined uncertainties and broader model comparisons are recommended.
Susmita Sarkar, Nayan Sarkar, Abhisek Dutta
et al.
In this article, we estimate the gravitational deflection angles of light in the spacetime of Einstein–Cartan wormholes supported by normal matter or phantom energy utilizing the Gauss–Bonnet theorem. The obtained deflection angles are examined in relation to the wormhole throat radius <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> and the equation of state parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> across four scenarios, and it has been seen that the larger throat radii <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> result in higher deflection angles. Moreover, the wormholes filled with phantom energy exhibit greater deflection angles compared to those filled with normal matter. The reported deflection angles are influenced by dark matter and Maxwell’s fish eye matter: Dark matter, as well as Maxwell’s fish eye matter, increases the deflection angles. The deflection angle is also estimated using the Keeton and Petters method, which is proportional to wormhole throat <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> and inversely proportional to the impact parameter <i>b</i>. Additionally, a comparative study is performed on the deflection angles obtained from four different scenarios. Finally, analytical results for time delay due to Einstein–Cartan wormholes are estimated for the four <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> cases which are decreasing for increasing values of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>c</mi></msub></semantics></math></inline-formula>.
The CMS collaboration, A. Tumasyan, W. Adam
et al.
Abstract The hydrodynamic flow-like behavior of charged hadrons in high-energy lead-lead collisions is studied through multiparticle correlations. The elliptic anisotropy values based on different orders of multiparticle cumulants, v 2{2k}, are measured up to the tenth order (k = 5) as functions of the collision centrality at a nucleon-nucleon center-of-mass energy of s NN $$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV. The data were recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 0.607 nb −1. A hierarchy is observed between the coefficients, with v 2{2} > v 2{4} ≳ v 2{6} ≳ v 2{8} ≳ v 2{10}. Based on these results, centrality-dependent moments for the fluctuation-driven event-by-event v 2 distribution are determined, including the skewness, kurtosis and, for the first time, superskewness. Assuming a hydrodynamic expansion of the produced medium, these moments directly probe the initial-state geometry in high-energy nucleus-nucleus collisions.
Nuclear and particle physics. Atomic energy. Radioactivity
Luca Schirru, Adelaide Ladu, Francesco Gaudiomonte
Radio frequency interference (RFI) represents all unwanted signals detected by radio receivers of a telescope. Unfortunately, the presence of RFI is significantly increasing with the technological development of wireless systems around the world. For this reason, RFI measurement campaigns are periodically necessary to map the RFI scenario around a telescope. The Sardinia Radio Telescope (SRT) is an Italian instrument that was designed to operate in a wide frequency band between 300 MHz and 116 GHz. One of the receivers of the telescope is a coaxial cryogenic receiver that covered a portion of the P and L bands (i.e., 305–410 MHz and 1300–1800 MHz) in its original version. Although the receiver was used for years to observe bright sources with sufficient results, its sub-bands can be redesigned considering the most recently evolved RFI scenario. In this paper, the results of a RFI measurement campaign are reported and discussed. On the basis of these results, the new sub-bands of the L-P receiver, together with the design of the new microwave filter selector block of the SRT receiver, are presented. In this way, SRT will cover up to 120 MHz and 460 MHz of −3 dB bandwidth at the P-band (290–410 MHz) and L-band (1320–1780 MHz), respectively. The bands of these filters are selected to reject the main RFI with high levels of amplitude and optimize the estimated antenna temperature and sensitivity of the receiver during the research activities, such as pulsar observations, very long baseline interferometer applications and spectroscopy science.
One of the recent attempts to address the Hubble and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>S</mi><mn>8</mn></msub></semantics></math></inline-formula> tensions is to consider that the Universe started out not as a de Sitter-like spacetime, but rather anti-de Sitter-like. That is, the Universe underwent an “AdS-to-dS” transition at some point. We study the possibility that there are two dark energy fluids, one of which gave rise to the anti-de Sitter-like early Universe. The interaction is modeled by the Lotka–Volterra equations commonly used in population biology. We consider “competition” models that are further classified as “unfair competition” and “fair competition”. The former involves a quintessence in competition with a phantom, and the second involves two phantom fluids. Surprisingly, even in the latter scenario it is possible for the overall dark energy to cross the phantom divide. The latter model also allows a constant <i>w</i> “AdS-to-dS” transition, thus evading the theorem that such a dark energy must possess a singular equation of state. We also consider a “conversion” model in which a phantom fluid still manages to achieve “AdS-to-dS” transition even if it is being converted into a negative energy density quintessence. In these models, the energy density of the late time effective dark energy is related to the coefficient of the quadratic self-interaction term of the fluids, which is analogous to the resource capacity in population biology.
There are two free coupling parameters <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>c</mi><mn>13</mn></msub></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>c</mi><mn>14</mn></msub></semantics></math></inline-formula> in the Einstein–Æther metric describing a non-rotating black hole. This metric is the Reissner–Nordström black hole solution when <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>≤</mo><mn>2</mn><msub><mi>c</mi><mn>13</mn></msub><mo><</mo><msub><mi>c</mi><mn>14</mn></msub><mo><</mo><mn>2</mn></mrow></semantics></math></inline-formula>, but it is not for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>≤</mo><msub><mi>c</mi><mn>14</mn></msub><mo><</mo><mn>2</mn><msub><mi>c</mi><mn>13</mn></msub><mo><</mo><mn>2</mn></mrow></semantics></math></inline-formula>. When the black hole is immersed in an external asymptotically uniform magnetic field, the Hamiltonian system describing the motion of charged particles around the black hole is not integrable; however, the Hamiltonian allows for the construction of explicit symplectic integrators. The proposed fourth-order explicit symplectic scheme is used to investigate the dynamics of charged particles because it exhibits excellent long-term performance in conserving the Hamiltonian. No universal rule can be given to the dependence of regular and chaotic dynamics on varying one or two parameters <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>c</mi><mn>13</mn></msub></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>c</mi><mn>14</mn></msub></semantics></math></inline-formula> in the two cases of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>≤</mo><mn>2</mn><msub><mi>c</mi><mn>13</mn></msub><mo><</mo><msub><mi>c</mi><mn>14</mn></msub><mo><</mo><mn>2</mn></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>≤</mo><msub><mi>c</mi><mn>14</mn></msub><mo><</mo><mn>2</mn><msub><mi>c</mi><mn>13</mn></msub><mo><</mo><mn>2</mn></mrow></semantics></math></inline-formula>. The distributions of order and chaos in the binary parameter space <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>(</mo><msub><mi>c</mi><mn>13</mn></msub><mo>,</mo><msub><mi>c</mi><mn>14</mn></msub><mo>)</mo></mrow></semantics></math></inline-formula> rely on different combinations of the other parameters and the initial conditions.
Galactic nuclei harbouring a central supermassive black hole (SMBH), possibly surrounded by a dense nuclear cluster (NC), represent extreme environments that house a complex interplay of many physical processes that uniquely affect stellar formation, evolution, and dynamics. The discovery of gravitational waves (GWs) emitted by merging black holes (BHs) and neutron stars (NSs), funnelled a huge amount of work focused on understanding how compact object binaries (COBs) can pair up and merge together. Here, we review from a theoretical standpoint how different mechanisms concur with the formation, evolution, and merger of COBs around quiescent SMBHs and active galactic nuclei (AGNs), summarising the main predictions for current and future (GW) detections and outlining the possible features that can clearly mark a galactic nuclei origin.
The <i>Kepler</i> space telescope has detected a large number of variable stars. We summarize 2261 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>δ</mi></semantics></math></inline-formula> Scuti and hybrid variables in the literature, and perform time-frequency analysis on these variable stars. Two non-eclipsing binary systems, KIC 5080290 and KIC 5480114, are newly discovered. They both pass more detailed aperture photometry and bright star contamination checks. The results of the time-frequency analysis demonstrate that the companions are stellar objects with orbital periods of approximately 265 days and 445 days, respectively. The orbital parameters of the two systems and the lower mass limits of the companions are obtained. The primary stars of both systems are slightly evolved intermediate-mass stars. The detection of intermediate-mass binary stars is helpful to understand the formation and evolution mechanism of binary stars in this mass region.
We discuss the thermalization process in kinetic approximation in the presence of non-zero initial anomalous quantum expectation values on top of an initial non-Planckian (non-thermal) level population. In particular, we derive a system of “kinetic” equations for the level population and anomalous expectation values in four-dimensional massive scalar field theory with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi>φ</mi><mn>4</mn></msup></semantics></math></inline-formula> self-interaction. We analytically show, in the linear approximation, that for their small initial values, the anomalous quantum averages relax down to zero. Furthermore, we show analytically that this system does not have an equilibrium solution with non-zero time independent anomalous expectation value.
A search for the dimuon decay of the Standard Model (SM) Higgs boson is performed using data corresponding to an integrated luminosity of 139 fb−1 collected with the ATLAS detector in Run 2 pp collisions at s=13 TeV at the Large Hadron Collider. The observed (expected) significance over the background-only hypothesis for a Higgs boson with a mass of 125.09 GeV is 2.0σ (1.7σ). The observed upper limit on the cross section times branching ratio for pp→H→μμ is 2.2 times the SM prediction at 95% confidence level, while the expected limit on a H→μμ signal assuming the absence (presence) of a SM signal is 1.1 (2.0). The best-fit value of the signal strength parameter, defined as the ratio of the observed signal yield to the one expected in the SM, is μ=1.2±0.6.