In this study, we analyze the temperature dependence of Exceptional Points (EPs) in a pseudo-Hermitian hybrid model composed of a superconducting flux qubit (SFQ) interacting with an ensemble of nitrogen-vacancy (NV) color centers in diamond [1–2]. This model is relevant not only due to its experimental realizability [1], but also as a representative example of a many-body Hamiltonian exhibiting a nontrivial interplay of distinct physical effects.

The interaction between the NV ensemble and the SFQ is modeled by introducing an asymmetry parameter [2] that modifies the balance between the creation and annihilation processes of NVs coupled to the SFQ. This asymmetry accounts for the presence of impurities within the NV ensemble, such as P1 centers [3].

As reported in [4], temperature effects on the zero-field splitting states of the NV ensemble are negligible below T=200 KT = 200~\mathrm{K}T=200 K. Therefore, we assume that temperature has an insignificant effect on the NV ensemble. This is not the case for the SFQ, as superconductivity is well known to be strongly temperature-dependent.

We investigate how the location of the EPs and the extent of each symmetry phase evolve with temperature by explicitly incorporating the temperature dependence of the superconducting gap in the SFQ . To characterize the system’s evolution and the impact of thermal effects, we analyze several observables, including the survival probability, expectation values of spin components, spin squeezing, and the SU(2) Wigner function. The initial state is prepared as a spin coherent state for the NV ensemble, with the SFQ in its ground state.

Our results show that increasing temperature tends to expand the region of parameter space corresponding to the exact-symmetry phase [5].

[1] X. Zhu et al., Nature 478, 211 (2011).

[2] R. Ramírez, M. Reboiro, and D. Tielas, The European Physical Journal D 74, 193 (2020).

[3] V. Stepanov and S. Takahashi, Phys. Rev. B 94, 024421 (2016).

[4] M. C. Cambria et al., Phys. Rev. B 108, L180102 (2023)

[5] to be published.

One of the canonical approaches to quantum gravity is quantum geometrodynamics. It arises from the quantization of Hamiltonian constraints. This method gives rise to the Wheeler–DeWitt equation, which can be solved in minisuperspace models to obtain the wavefunction of the universe. Despite its long history, this approach still faces fundamental challenges: operator ordering ambiguity, the problem of time, and the lack of a clear probabilistic interpretation remain open issues. In our work, we discuss how studies of entropy may shed some light on these difficulties.

We study a toy model of the Wheeler–DeWitt equation for a Friedmann–Lemaître–Robertson–Walker (FLRW) universe with a non-zero cosmological constant and matter content consisting of a massive scalar field coupled to gravity. We construct the universal wavefunction using a spectral expansion method, which allows us to obtain numerical solutions on the entire domain while avoiding instabilities. This approach enables a detailed analysis of the wavefunction and provides access to both gravitational and matter degrees of freedom without the use of the slow-roll approximation.

Based on the obtained universal wavefunction, we discuss possible entropy measures and their implications, as well as the potential role of matter–geometry entanglement as an indicator of the quantum-to-classical transition. We conclude with a comment on the use of entropy-related quantities as arrows of time.

Rotating traversable wormholes allow the effects of frame-dragging and rotation to be
studied in the absence of event horizons. We develop a quantum field-theoretic treatment of massless scalar perturbations in the rotating Teo spacetime (an exact, stationary,
horizonless, traversable wormhole with two asymptotically flat regions). Using the
Bogoliubov transformation formalism, we construct “in” and “out” mode solutions in the
two asymptotic regions and compute the Bogoliubov coefficients (αωm,βωm) that quantify
mode mixing.
The effective radial potential induced by rotation and frame-dragging forms an
asymmetric scattering barrier. This asymmetry permits an exact analytic evaluation of
reflection and transmission amplitudes via the barrier penetration exponent, yielding
closed-form expressions for the Bogoliubov coefficients, mean particle number,
superradiant amplification, and the two-mode entanglement entropy Sωm as functions of
the rotation parameter a.
Because the spacetime is stationary, particle creation and amplification arise purely from
geometric asymmetry rather than explicit time-dependence. Co-rotating and
counter-rotating modes experience inequivalent scattering, rendering the process
intrinsically non-reciprocal. We thus identify a stationary geometric analog of the recently
proposed Asymmetric Dynamical Casimir Effect, in which rotation and frame-dragging
replace moving boundaries as the source of asymmetric mode mixing.
Our results unify classical superradiant scattering, quantum Bogoliubov amplification, and
asymmetric Casimir physics within a single horizonless geometry, demonstrating that
neither horizons nor time-dependent metrics are necessary for quantum particle creation
from the vacuum. The framework opens the door to future studies of higher-spin fields,
slowly varying rotation, and semiclassical backreaction effects.

At quantum scales, the classical description of spacetime no longer holds: the metric tensor develops intrinsic quantum fluctuations and cannot be treated as a smooth continuous field. Consequently, a black hole horizon also fails to remain an ideal smooth null hypersurface. Instead, it acquires quantum “wiggles,” corresponding to soft degrees of freedom—low-energy excitations capable of storing information as soft hair. These irregularities prevent the horizon from acting as a smooth two-dimensional surface at the Planck scale, giving it a highly jagged or fractal character. To model this deviation from smoothness, Barrow [Phys. Lett. B 808 (2020) 135643] proposed that the horizon is described by a fractal dimension, d=2+Δ , 0<Δ<1, with Δ quantifying the geometric deformation. For such a surface, the effective area scales as Aeff∝Rgd, instead of the classical A_{Cls}∝(R_g)^d. Based on the Bekenstein–Hawking argument that entropy counts horizon-covering Planck cells, this fractal surface increases the microscopic degrees of freedom, leading to the modified Barrow entropy S_B∝(A / A_{Pl})(1+Δ/2). Using the first law dM=T_BdS_B​, the corresponding temperature becomes a multiple of T_H. The heat capacity remains negative for all 0<Δ<1, so the thermodynamic instability of the Schwarzschild black hole persists. However, the reduced temperature suggests a slower evaporation process and the possible formation of a long-lived remnant. Geometrothermodynamics is reconstructed using this new fractalized entropy.

When excited states decay with energy $E_0-i\Gamma$, the time evolution operator $U(t)=e^{-iHt}$ does not obey $U^{\dagger}(t)U(t)=I$. Nonetheless, probability conservation is not lost if one includes both decay and excitation with energy $E_0+i\Gamma$, though it takes a different form. Specifically, if the eigenspectrum of a Hamiltonian is complete, then due to $CPT$ symmetry, a symmetry that holds for all physical systems, there must exist an operator $V$ that effects $VHV^{-1}=H^{\dagger}$, so that $V^{-1}U^{\dagger}(t)VU(t)=I$. As a consequence, because of probability conservation, the time delay associated with decay must be accompanied by an equal and opposite time advance for excitation. Thus, when a photon excites an atom, the spontaneous emission of a photon from the excited state must occur without any decay time delay at all. An effect of this form, together with an associated negative time delay, have recently been reported by Sinclair et al., PRX Quantum 3, 010314 (2022), and Angulo et al., arXiv:2409.03680 [quant-ph]. We show that the non-relativistic square well problem with a real potential possesses $PT$ symmetry in both the bound and scattering sectors, with complex conjugate pairs of energy eigenvalues in the scattering sector. In addition, we show that the square well scattering threshold branch point is an exceptional point (a characteristic of systems with an antilinear symmetry such as $PT$), a point at which the Hamiltonian becomes of non-diagonalizable, and thus manifestly non-Hermitian, Jordan-block form. The square well potential, one of the oldest known quantum-mechanical systems, provides an explicit realization of how antlinearity is more general than Hermiticity.

References:

Phys. Rev. D 112, L031903 (2025). (arXiv:2504.12068 [quant-ph]).

ArXiv: 2505.07798 {quant-ph].

Quantum biology is an emerging interdisciplinary field that investigates the fundamental quantum mechanisms underlying biological processes and their potential roles in the emergence and sustainability of life beyond Earth. While classical biochemistry successfully describes many aspects of life, experimental and theoretical evidence increasingly suggests that quantum effects such as coherence, tunneling, and entanglement play crucial roles in processes such as photosynthesis, enzyme catalysis, olfaction, and magnetoreception. In photosynthesis, energy transfer occurs through quantum coherence in pigment–protein complexes, while enzyme catalysis can involve proton or electron tunneling. Olfactory sensing may rely on electron tunneling, and magnetoreception in birds involves spin dynamics and entanglement in cryptochrome proteins. This work provides an in-depth analysis of these mechanisms, emphasizing how they might operate under cosmic conditions, including extreme temperatures, high-radiation, microgravity, and low-energy environments. Understanding these processes offers insights into the limits of quantum coherence in extreme environments, the potential emergence of life in diverse planetary and interstellar settings, and the fundamental principles governing complex systems. Additionally, potential applications in quantum-inspired technologies and biomimetic systems are discussed, highlighting how principles observed in living organisms can guide the design of novel quantum devices. By examining quantum mechanisms in both terrestrial and cosmic contexts, this work bridges physics, biology, and astrobiology, emphasizing the universal relevance of quantum principles to life across the cosmos.

Despite appealing theoretical features, higher time-derivative theories (HTDTs) are notoriously plagued by issues of instability—most prominently the emergence of ghost states, which signal the presence of unbounded-from-below Hamiltonians or non-normalisable states, that threaten the physical viability of these theories. Consequently, the construction of ghost-free representations is a central aim.

The Pais–Uhlenbeck (PU) model, a canonical example of a fourth-order differential system, is a paradigmatic example of an HTDT and encapsulates their essential challenges and features. Using its multi-Hamiltonian structures in conjunction with the Lie symmetries of the dynamical equation, one can construct distinct, but compatible, Poisson bracket formulations that preserve the system’s dynamics. Amongst other possibilities, this framework allows the recasting of models in a positive definite manner while leaving the dynamical flow unchanged, thus resolving the ghost problem. The application of the outlined approach has successfully demonstrated the construction of ghost-free representatives for the PU theory.

Introducing interactions to HTDTs generally challenges their stability further and poses a difficult problem. Going beyond the PU model, we here analyse an interacting extension of the system that admits closed-form solutions. This model suggests promising directions for the systematic construction of stable interacting HTDTs, future generalisations to field-theoretic settings, and further investigation into the quantisation of positive-definite PU models. A connection to an integrable realisation of the generalised Hénon–Heiles system (tied to Lax’s fifth-order KdV flow) is discussed.

In Situ Resource Utilization (ISRU 1,2) activities including local material based building works are planned for the missions targeting the Moon and Mars, as well as rare extraction from asteroids (3). Although preparation for such missions are going on, interaction and collaborative work between architects, engineers, Earth and planetary scientists have not been well formulated yet. To support such synergic activities, under the EU funded ArchiSpace project (101183089) a joint glossary is being developed to see how researchers from these different domains consider the same basic terms.

Using literature survey a first list as a glossary is presented, containing both architecture, engineering, Earth and planetary science topics. Using the knowledge of the community and the general view, several important comparative aspects have been considered. The terms used in this glossary are accompanied with related aspects of classical architecture and engineering domains, as well as their corresponding information from Earth and planetary science.

There are specific meanings for almost all considered terms at the four different domains with focusing on the characteristics relevant to the given topic. Corresponding links are present between the versions how different domains consider a given key term (like soil, cementation, compaction etc.). The specific terms related knowledge between the different domains could be interconnected, however the information transfer between them is not straightforward and requires further improvement. Such transfer of information between these key terms can be supported by numerical values (density, adhesion, composition, grain size etc.), which should be tested by case studies for Moon and Mars surface habitat planning. The glossary will be presented at the meeting and the ongoing work welcomes contributors from various but mainly the architecture and engineering related topics.

References: (1) Jared et al. 2026. Planetary and Space Science 270, id.106229. (2) Gross et al. 2024. Acta Astronautica 223, 15-24. (3) Trigo-Rodríguez et al. MNRAS 545(1), staf1902

The detection of exocomets provides a unique window into the small-body populations and dynamical evolution of extrasolar planetary systems. While spectroscopic signatures of exocomets have been identified in several debris-disk systems (e.g. Ferlet et al. 1987; Kiefer et al. 2014), photometric detections remain relatively rare and challenging due to their transient, asymmetric, and often aperiodic nature. However, previous studies have shown that exocomet transits can produce characteristic light-curve signatures that are, in principle, detectable in high-precision photometric data (Lecavelier des Etangs et al. 1999; Rappaport et al. 2018).

We explore simplified models of dusty exocomet transits, focusing on how different cometary structures may influence the observed shape of stellar light curves. The study relies on numerical simulations to examine the combined effects of absorption and scattering by circumstellar dust across a range of wavelengths. By considering various plausible dust properties and observing configurations, we aim to assess which photometric features could serve as reliable indicators of exocometary activity in transit observations (Kálmán et al. 2024).

The resulting synthetic light curves reproduce the characteristic asymmetric “shark-fin” transit profiles associated with exocomets, while revealing a strong wavelength dependence driven by dust properties. We show that multi-band photometry significantly enhances the ability to distinguish exocomet transits from other aperiodic dimming events, such as stellar activity or circumstellar disk structures. In particular, color-dependent transit depths and timing shifts provide constraints on grain size evolution and material composition within the cometary tail.

This work highlights the potential of exocomet transit simulations as a useful tool for interpreting photometric observations and for guiding future searches for exocomets. In particular, upcoming missions such as ARIEL, with its multi-wavelength observing capabilities, may offer new opportunities to identify and characterise dusty cometary transits in extrasolar systems (Tinetti et al. 2021).

3I/ATLAS is the third interstellar object identified crossing our solar system, and the second one exhibiting a cometary appearance. Pre-and post-perihelion photometric observations, inner coma imagery, and a spectroscopic comparison with CR and CH carbonaceous chondrites will be presented. The spectral similarities found are consistent with 3I/ATLAS, being a carbonaceous object, likely enriched in native metal and undergoing significant aqueous alteration during its approach to the Sun, like the hydrated chondrites widely observed in the Solar System(Trigo-Rodríguez et al., 2019). The extensive corrosion experienced due to its porous nature and the presence of reactive minerals, experiencing energetic Fischer–Tropsch reactions, makes it develop a new kind of cryovulcanism, similar to the pristine Trans-Neptunian Objects in our own planetary system. We proposed that the combination of elevated metal abundance and abundant water and ice can account for the unusual coma morphology and chemical products reported to date, particularly the overabundance of Ni in the coma (Trigo-Rodríguez et al. 2025). In consequence, the study of interstellar objects such as 3I/ATLAS, gravitationally scattered eons ago, provides unique opportunities to study physico-chemical processes occurred in minor bodies of our own Solar System, including transitional bodies similar to trans-Neptunian objects from the Solar System. I envision that the ESA's planned Comet Interceptor mission, and future sample return missions to new interstellar visitors exhibiting DeltaV favorable encounter conditions, can provide a pleyade of new information on the formation of planetary systems across our galaxy. Given the extraordinary catalytic potential of carbonaceous chondrites to promote complex organics under aqueous alteration (Rotelli et al., 2016), such discoveries could promote a significant breakthrough in our knowledge on the ubiquity of organic life in the Universe.

References:

Rotelli L. et al. (2016) Nature Sci. Rep., 6:38888.

Trigo-Rodríguez J. et al. (2019) Space Sci. Rev. 215:18, 27 pp.

Trigo-Rodríguez, J. et al. (2025) ArXiv: 2511.19112