The Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) dilatonic black hole, a key solution in low-energy string theory, exhibits previously unexplored chaotic dynamics for charged test particles under electromagnetic influence. While characterizing such chaos requires high-precision numerical methods, our prior research identifies the explicit symplectic algorithm as the optimal integration tool for strongly curved gravitational systems. Leveraging the Hamiltonian formulation of the GMGHS black hole, we develop an optimized fourth-order symplectic algorithm, <math altimg='si28.svg'><mrow><mi>P</mi><mi>R</mi><msub><mi>K</mi><mn>6</mn></msub><mn>4</mn></mrow></math>. This algorithm enables a systematic investigation of chaotic motion using four distinct chaos indicators: the Shannon entropy, Poincar&#233; sections, the maximum Lyapunov exponent, and the Fast Lyapunov Indicator. Our results demonstrate a critical dependence of chaos on both electric charge ( <math altimg='si1.svg'><mi>Q</mi></math>, characterized by the Coulomb parameter <math altimg='si11.svg'><msup><mi>Q</mi><mo>*</mo></msup></math>) and magnetic charge ( <math altimg='si17.svg'><msub><mi>Q</mi><mi>m</mi></msub></math>). Specifically, in electrically charged backgrounds, order-to-chaos transitions occur with increasing <math altimg='si1.svg'><mi>Q</mi></math>. Conversely, in magnetically charged backgrounds, chaos emerges with increasing <math altimg='si17.svg'><msub><mi>Q</mi><mi>m</mi></msub></math>. When <math altimg='si1.svg'><mi>Q</mi></math> and <math altimg='si11.svg'><msup><mi>Q</mi><mo>*</mo></msup></math> vary simultaneously, the chaotic dynamics exhibit greater sensitivity to changes in <math altimg='si11.svg'><msup><mi>Q</mi><mo>*</mo></msup></math>. Especially, these findings establish the Shannon entropy as a robust chaos indicator within relativistic frameworks and provide novel insights into the dynamics of string-theoretic black holes.

China

Zhen-Meng Xu

Da-Zhu Ma

Kai Li

Chaos dynamics of charged particles near Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes

We consider a disordered system of interacting fermions, for which we demonstrate, that depending on the relationship between the degree of disorder and real physical dimensionality <italic>d</italic>, this system undergoes a delocalization (e.g. a metal-insulator) phase transition. The effect of the disorder is accounted for by replacing the ordinary single-particle kinetic energy operator by that with a fractional spectrum. These fractional spectra represent the microscopic equivalent of the well-known non-trivial power-law decay of the low-energy density of states of non-interacting disordered systems. We develop a powerful approach to analyze the density of states in interacting disordered system, combining both the saddle-point and renormalization group methods. These two methods complement each other effectively. Through this approach, we identify a fixed point in the renormalization group flow of the model&#8217;s parameters, which dictates the behavior of the system in the conducting phase. Additionally, we extend our analysis to include static conductivity. Our examination of the system&#8217;s conductivity allows us to establish several strict conditions regarding the stability of the metallic state across different spatial dimensions <italic>d</italic>. Notably, we emphasize the unique significance of the two-dimensional case <math altimg='si13.svg'><mrow><mi>d</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math>. We also compare our findings with salient experimental features observed in paradigmatic physical systems.

Poland

A. Sinner

V.A. Stephanovich

B. Pytel

A. Wójcik

Fractional spectrum due to disorder and its effect on the ground state in the ensembles of interacting fermions

Using Newton s stellar balance equation in conjunction with the observed flat rotation velocities of satellite galaxies, we estimate the speed of sound in a dark matter medium. Our analysis reveals that the orbital velocities of these satellite galaxies significantly exceed the calculated sound speed. This disparity implies that the satellites traverse the dark matter medium at supersonic speeds, thereby giving rise to shock waves within it.Our observational study also supports this conclusion by examining nine spiral galaxies, where we consistently find that the inclination-corrected flat rotation velocities ( <math altimg='si1.svg'><msub><mi>V</mi><mrow><mi mathvariant='normal'>flat</mi></mrow></msub></math>) surpass the dark matter sound speeds (cs). This disparity holds across a range of dark matter surface densities, demonstrating that supersonic motion and consequent shock wave generation are robust features in diverse galactic environments.

India

Mofazzal Azam

M. Sami

Farook Rahaman

Anikul Islam

Aritra Sanyal

Romania

Irina Radinschi

An observation on shock waves in a dark matter medium

We continue our study of fractionally charged particles (FCPs)—particles carrying electric charge a multiple of <math altimg='si44.svg'><mrow><mi>e</mi><mo linebreak='goodbreak'>/</mo><mn>6</mn></mrow></math>. Discovering an FCP would inform us about both Standard Model physics (what the true gauge group and the one-form global symmetry are) and Beyond the Standard Model physics (ruling out many unified theories), which makes them a high-stakes target for collider searches. Here we find that with two FCPs there are vastly richer phenomenologies compared to the single-particle extensions we previously studied. Stringent constraints on colored FCPs can be dramatically weakened when decays are open; conversely the cross sections of the least visible species can be enlarged by up to <math altimg='si45.svg'><mrow><mo>&#8764;</mo><msup><mn>10</mn><mn>3</mn></msup></mrow></math>, increasing their discovery potential enormously at the LHC and milliQan. Overall, these simple models motivate performing searches for FCPs produced along with jets or leptons, and highlight &#8216;free&#8217; discovery potential in reanalyzing existing missing-energy datasets for low-quality tracks.

United States

Seth Koren

Adam Martin

Phenomenology of fractionally charged particles: Two reps are better than one

We discuss a set of precision observables that can probe the existence of a light particle <math altimg='si6.svg'><mi>X</mi></math> coupled to electrons in the mass range of 1&#8211;100 MeV. As a case study, we consider the recent excess of <math altimg='si7.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup></mrow></math> final-state events at <math altimg='si8.svg'><mrow><msqrt><mi>s</mi></msqrt><mo linebreak='goodbreak'>=</mo><mn>16.9</mn></mrow></math> MeV reported by the PADME collaboration. Interestingly, this mass is tantalizingly close to the invariant mass at which anomalous <math altimg='si7.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup></mrow></math> pair production has previously been observed in nuclear transitions from excited to ground states by the ATOMKI collaboration. For the scenario in which the new particle has a vector coupling to electrons, we show that the PADME excess is already in tension with constraints from the anomalous magnetic moment of the electron. Further improvements in the measurement of the electron <math altimg='si9.svg'><mi>g</mi></math>-2, together with upcoming results from PIONEER (searching for <math altimg='si10.svg'><mrow><msup><mi>&#960;</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>e</mi><mo>+</mo></msup><mi>&#957;</mi><mi>X</mi></mrow></math>) and Mu3e (searching for <math altimg='si11.svg'><mrow><msup><mi>&#956;</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>e</mi><mo>+</mo></msup><msub><mover><mrow><mi>&#957;</mi></mrow><mo stretchy='true'>&#8254;</mo></mover><mi>&#956;</mi></msub><msub><mi>&#957;</mi><mi>e</mi></msub><mi>X</mi></mrow></math>), are expected to definitively probe this scenario in the near future. We also explore alternative possibilities where the new particle has scalar, pseudoscalar, or axial-vector couplings.

Italy

Luca Di Luzio

Paride Paradisi

Nudžeim Selimović

Hunting for a 17 MeV particle coupled to electrons

In this paper, we investigate the dynamics of neutral test particles in the background of a non-rotating quantum Oppenheimer-Snyder black hole (BH) with a positive cosmological constant, an effective spacetime derived from loop quantum gravity corrections to classical gravitational collapse. The spacetime metric is characterized by a quantum correction parameter <italic>&#946;</italic>, mass <italic>M</italic>, and cosmological constant &#923;, which together modify the near-horizon geometry and yield a minimum BH mass threshold absent in classical GR. We analyze the effective potential governing particle motion and demonstrate how <italic>&#946;</italic> influences the stability of orbits, the location of the innermost stable circular orbits (ISCOs), and the associated conserved quantities. Our results show that increasing quantum corrections shifts the ISCOs radius inward, allowing stable orbits closer to the horizon, while decreasing the energy and angular momentum of circular trajectories. We provide the constraints on the parameters involved by using the shadow radius. Perturbations around circular motion are studied to derive epicyclic frequencies, which describe small radial and vertical oscillations and are central to quasi-periodic oscillations (QPOs) models observed in accreting compact objects. We compute these oscillatory frequencies as measured by both local and distant observers and explore the periastron precession frequency as a function of the quantum parameter. In addition, the analysis reveals that quantum effects significantly modify the profiles of epicyclic frequencies and precession, potentially leaving observable imprints in the timing properties of astrophysical accretion systems.

Algeria

Abdelmalek Bouzenada

Azerbaijan

Asifa Ashraf

Uzbekistan

Farruh Atamurotov

Ikhtiyor Saidov

Saudi Arabia

Tahani Mohammed Alrosaa

Arafa A. Yagob

Particle dynamics and quasi-periodic oscillations around quantum Oppenheimer-Snyder de Sitter black hole

The Generalized Uncertainty Principle (GUP) extends the Heisenberg Uncertainty Principle (HUP) by suggesting a minimum observable scale that includes the effects of quantum gravity, which is supposed to potentially result in observable effects far below the Planck energy scale, providing us the opportunity to explore the theory of quantum gravity through physical processes at low energy scale. In present work, we study the corrections induced by the GUP to the spontaneous radiation properties of a two-level atom interacting with a real massless scalar quantum field based on the DDC formalism. The GUP alters the correlation function of the scalar field, consequently affecting the radiative properties of atoms. We calculate the rate of change in the mean atomic energy for an atom undergoing inertial motion, uniform acceleration, and uniform circular motion. We show that the GUP can modify the spontaneous emission rate of an excited-state atom in inertial motion; however, it does not alter the stability of the ground-state atom in vacuum. For an atom in uniformly accelerated and uniformly circular motions, the GUP can change both its spontaneous emission and excitation rates; moreover, the corrections caused by the GUP contains the terms proportional to <math altimg='si7.svg'><mrow><mi>&#946;</mi><msup><mi>a</mi><mn>2</mn></msup></mrow></math> or <math altimg='si8.svg'><mrow><mi>&#946;</mi><msup><mi>a</mi><mn>3</mn></msup></mrow></math>, suggesting that the proper acceleration <math altimg='si9.svg'><mi>a</mi></math> of an atom in non-inertial motions could significantly amplify the effect of the GUP on the spontaneous transition rates of the atom.

Zhi Wang

Quantum gravity corrections to the spontaneous excitation of an accelerated atom interacting with a quantum scalar field

In this paper, we investigate the circuit complexity of a quantum harmonic oscillator subjected to an external magnetic field. Utilizing the Nielsen approach within the thermofield dynamics (TFD) framework, we determine the complexity of thermofield double states as functions of time, temperature, and the external magnetic field. Our subsequent analysis reveals various features of this complexity. For instance, as temperature increases, the amplitude of complexity oscillations also rises, while at low temperatures, complexity stabilizes at a constant positive value. Furthermore, the magnetic field creates two distinct sectors: strong magnetic fields exhibit periodic complexity oscillations, whereas weak magnetic fields induce a beating effect. Finally, we confirm that the rate of complexity obeys the Lloyd bound.

Bulgaria

V. Avramov

M. Radomirov

Austria

R.C. Rashkov

T. Vetsov

Thermal quantum harmonic oscillator under magnetic field: A complexity approach

In a talk at an IHEP-Beijing symposium celebrating the 50th anniversary of the discovery of the <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math>, I reminisced about some of the interesting phenomena that were observed in <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> decays in the BES, BESII, and BESIII detectors during the 35 year long BES experimental program. The three order of magnitude increase in the <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> event samples and the improved detector capabilities that occurred during this time led to a persistent series of interesting discoveries and new insights. As more <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> events were collected, the scientific interest in them increased and the breadth of physics topics that are addressed by them expanded. In addition, I speculated on what might happen if, in the next few decades, the magnitude of <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> data samples and the detector capabilities continued to increase at similar paces. In particular, I emphasize the possibilities of searches for <math altimg='si111.svg'><mi mathvariant='script'>C</mi></math> <math altimg='si112.svg'><mi mathvariant='script'>P</mi></math> violation in strange hyperon decays and testing the <math altimg='si111.svg'><mi mathvariant='script'>C</mi></math> <math altimg='si112.svg'><mi mathvariant='script'>P</mi></math> <math altimg='si113.svg'><mi mathvariant='script'>T</mi></math> theorem with strangeness-tagged neutral kaon decays.

South Korea

Stephen Lars Olsen

You never have enough <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> events - The case for a <math altimg='si3.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>/</mo><mi>&#968;</mi></mrow></math> factory

In this study, we investigate the motion of neutral test particles in the space-time of a spherically symmetric charged Horndeski black hole. By employing the effective potential method, we analyze the conditions for the stability of circular orbits confined to the equatorial plane. Explicit mathematical relations for the energy and angular momentum of test particles are obtained as functions of the black hole parameters, highlighting the role of charge and scalar coupling in orbital dynamics. We further examine the behavior of the effective force exerted on the particles and determine the position of the innermost stable circular orbit. To complement the analytical results, we numerically solve the equations of motion and visualize the trajectories of test particles under different configurations. The study is extended to include small perturbations around stable orbits, from which we derive the radial, polar, and azimuthal epicyclic frequencies. Additionally, we compute the periastron precession frequency and explore its dependence on black hole parameters. The overall analysis demonstrates that the dynamical properties of particles are highly sensitive to the characteristics of the black hole, offering deeper insights into the influence of Horndeski modifications on relativistic motion.

Pakistan

Tayyab Nasser

Allah Ditta

Kashif Ammar Yasir

Oman

S.K. Maurya

Gulzoda Rakhimova

Analyzing QPOs and dynamics with trajectories around charged Horndeski black hole