The origin of the large-scale magnetic fields permeating the Universe and the nature of dark matter are two of the most enduring open questions in modern cosmology. In this work, we investigate a unified early-universe scenario in which both phenomena arise naturally from a single primordial magnetogenesis mechanism. We show that the generation of primordial magnetic fields during the post-inflationary era not only provides seeds for the coherent magnetic fields observed today on cosmological scales, but also enhances curvature perturbations at intermediate wavelengths. These amplified perturbations become sufficiently large to trigger the formation of primordial black holes (PBHs), which can contribute substantially—if not dominantly—to the present dark-matter abundance. The same enhanced scalar fluctuations responsible for PBH formation inevitably induce a stochastic background of gravitational waves (GWs). We analyze the spectral features of this induced GW background and demonstrate that it carries a detailed imprint of the underlying magnetogenesis model and the expansion history of the Universe, particularly during non-standard reheating phases. By combining constraints from large-scale magnetic fields, PBH abundances, and induced GWs, we establish a powerful multi-messenger approach for probing the physics of the early Universe.
Furthermore, we highlight how upcoming and next-generation gravitational-wave detectors—such as LISA, DECIGO, BBO, and the SKA pulsar-timing array—can measure or tightly constrain the predicted GW signal. Such observations offer a unique opportunity to reconstruct the spectral behavior of the induced GWs and thereby uncover information about the reheating dynamics and the primordial magnetic field spectrum. Our results emphasize that jointly analyzing electromagnetic, gravitational-wave, and early-universe cosmological signatures provides an exceptionally sensitive pathway to uncovering the mechanisms that shaped cosmic magnetism and the origin of dark matter.

As was shown by Ellis in gr-qc/0411096, one can establish a correspondence between the Schwarzschild metric and a warp drive-type metric, making it possible to consider a warp drive in a black hole background. We elaborate upon this result and demonstrate that the black hole’s gravitational field can alleviate the violations of energy conditions, reducing the amount of negative energy required to sustain a warp bubble. Besides, we demonstrate that the black hole horizon is effectively absent for the observers inside the bubble, making it possible for them to send a light signal from the inside to the outside; however, the front wall of the warp bubble would emit Hawking radiation, possibly making the bubble unstable. The warp bubble would also possibly increase the black hole's entropy.

We also generalize the Ellis scheme to the case of Morris-Thorne wormholes and prove that Alcubierre warp drives cannot traverse humanly traversable wormholes and can only pass through those that either have a horizon or violate the flare-out condition. In addition, we consider warp drives in a de Sitter universe, and demonstrate that in this case, it's possible to interpret the warp bubble just as rearrangement of vacuum energy, in contract to exotic "negative energy". We discuss the implications of our results.

The 2012 landmark discovery of the Higgs boson by the ATLAS and CMS experiments marked the beginning of the new era for the LHC to precisely characterise this particle to validate and push the boundaries of the Standard Model through exploration at the highest available energies. To fully exploit the scientific potential of the LHC, both the accelerator and its detectors are undergoing extensive upgrades as part of the High-Luminosity LHC (HL-LHC) project, corresponding to an expected number of 140 to 200 simultaneous proton–proton interactions per bunch crossing by the end of the decade. A central element of this effort is the reinforcement of the forward muon system, for which CMS is deploying three new GEM-based muon stations: GE1/1, GE2/1, and ME0. These detectors combine excellent spatial resolution (∼250 μm), high-rate capability (>1 kHz/cm²), and radiation tolerance, while providing additional coordinate measurements and redundancy in combination with the existing Cathode Strip Chambers (CSCs) and RPCs. The GE1/1 station consists of 144 triple-GEM modules, arranged in super-chambers in both CMS endcaps, covering the range 1.55 < ∣η∣ < 2.18. The GE2/1 station, with 72 GEM chambers composed of 288 modules, extends coverage approximately over 1.62 < ∣η∣ < 2.43. The six-layer ME0 station, covering approximately 60 m², will be installed behind the new high-granularity calorimeter (HGCAL) during the third Long Shutdown (LS3) and will extend the CMS muon system’s pseudo-rapidity coverage from |η| < 2.4 to |η| < 2.8. Full system of GE1/1 and a few GE2/1 stations are contributing to the data taking in Run-3 with an operational efficiency above 95%. GEM technology efficiently rejects background and improves the precision of the muon bending angle measurement. This work presents an overview of the muon spectrometer upgrade of the CMS with GEM detectors, including operational experience and performance of the GEM station.

Galactic cosmic rays (GCRs) are continuously propagating high-energy charged particles originating outside the Solar System, whose intensity near Earth is significantly modulated by solar activity. One of the most prominent manifestations of this modulation is the transient reduction in GCR intensity known as a Forbush decrease (FD), which typically occurs in association with coronal mass ejections (CMEs), interplanetary shocks, and solar flare activity. This paper provides a comprehensive review of the primary physical mechanisms responsible for the suppression of cosmic ray flux during FD events. These mechanisms include magnetic shielding caused by enhanced interplanetary magnetic fields embedded within CMEs, shock-driven disturbances, and increased turbulence in the heliosphere. Observational data obtained from ground-based neutron monitor networks and space-borne instruments are analyzed to illustrate typical FD temporal profiles, recovery phases, and amplitude variations. The observed decreases in cosmic ray intensity generally range from approximately 3% for weak events to more than 20% for strong solar disturbances. Four illustrative figures are presented, showing characteristic FD events, schematic diagrams of CME–Earth interactions, shock structures, and large-scale heliospheric magnetic field configurations. The results emphasize the dominant role of strengthened interplanetary magnetic fields in deflecting and scattering low-energy GCRs, thereby reducing their access to the inner heliosphere. This study contributes to a deeper understanding of cosmic ray modulation processes and their relevance to space weather forecasting and heliophysical research.

We investigate the phenomenological aspects of a feebly interacting sterile neutrino dark matter candidate within a low-scale seesaw framework. The Type-I seesaw model is augmented by a second complex scalar doublet ($\Phi_{\nu}$), which couples exclusively to the heavy right-handed neutrinos and the lepton doublet, thereby generating the neutrino Dirac mass term while the first scalar doublet is responsible for giving mass to the remaining Standard Model particles.
The lightest sterile neutrino ($N_1$) acts as a feebly interacting massive particle (FIMP), produced via decays of $W^\pm$, $Z$ and extra scalars present in the setup. We point out that $W^\pm$ and $Z$ contributions were overlooked in the previous studies, which actually dominate the $N_1$ production by a factor of $\sim 10^{13}$ and solely determines the relic abundance. Incorporating them leads to several novel consequences for the DM phenomenology like a new non-thermal condition which leads to smaller Yukawa couplings. We thoroughly discuss the enhancement possibilities of $N_1$'s mass, which is controlled by the small vacuum expectation value ($v_{\nu}$) of the second Higgs doublet. After incorporating the latest Lyman-$\alpha$ forest observations, this setup can accommodate both warm and cold dark matter scenarios. We also discussed the dominant role of SM gauge bosons in dark matter production through heavy-light mixing ($V_{ij} = \frac{M_{D_{ij}}}{M_{N_{j}}}$), which leads to interactions between the heavy right-handed neutrinos with the $W$ and $Z$ bosons. In the context of the FIMP scenario, however, the dark matter couplings are inherently required to be extremely small to remain out-of-equilibrium. So, the out-of-equilibrium condition is the holy grail of the freeze-in mechanism.