The long-standing discrepancy of the muon anomalous magnetic moment ($g-2$) is a hint of new physics beyond the standard model of particle physics. In this paper, we show that heavy new physics contribution can be fully tested at a muon collider with a center-of-mass energy up to $\mathcal{O}(10)\mathrm{TeV}$ with $\mathcal{O}(10){\mathrm{ab}}^{-1}$. Even if there is no new particle in this energy range, one can measure the $g-2$ operator directly via the channel to a Higgs boson and a monochromatic photon. In particular, the latter process, which is the most challenging case, can be tested in the $20[50]\times (\frac{L_i}{40{\mathrm{ab}}^{-1}}{)}^{-1/2}\mathrm{TeV}$ muon collider at the 2 [5] $\sigma$ level with $L_i$ being the integrated luminosity if the efficiency of the detector built in the future is almost perfect.

Using a novel relation between the parity-even and -odd parts of a correlator, we show that the three-point function of conserved or weakly broken currents in three-dimensional conformal field theory (CFT) can be obtained from just the free fermion (FF) or the free boson (FB) theory. In the special case of large $N$ Chern-Simons matter theories, we obtain the correlator in terms of a coupling constant dependent “anyonic phase” factor. This anyonic phase factor was previously obtained in the $2\to 2$ exact S-matrix result and is consistent with strong-weak duality. By varying the coupling constant, the CFT correlator interpolates nicely between the same in the FF and FB theories.

A static observer with a finite lifetime has causal access to only a limited region of spacetime known as the causal diamond. The presence of an apparent horizon in the causal diamond, due to the observer’s finite lifetime, is the origin of an Unruh-like thermal effect. Thus, even though the observer is static and the background is flat, the finite-lifetime observer experiences a thermal bath in the Minkowski vacuum. In this article, we provide an open quantum systems approach that yields a complete thermal characterization via the observer’s steady-state density matrix, which is shown to be thermal with a temperature inversely proportional to its lifetime. This associated diamond temperature agrees with the established result derived from other methods. Moreover, our approach is particularly useful for designing entanglement harvesting protocols in the causal diamond. In addition, we introduce an insightful procedure that defines diamond coordinates using conformal transformations, and which leads to a more direct derivation of the thermal properties.

Motivated by recent experimental progress, we study scalar wave propagation over an imperfect draining vortex, which can serve as an analog for rotating and nonrotating extreme compact objects (ECOs). We encapsulate the absorbing properties of the analog ECO by means of an effective boundary located around the analog horizon. The presence of reflection at the effective boundary, characterized by a single parameter $\mathcal{K}$, allows for the existence of bound states located between the effective vortex core and the angular momentum barrier. The existence of these bound states leads to an enhanced absorption when the frequency of the incoming wave matches bound state frequencies, which result in Breit-Wigner type spectral lines in the absorption spectra. We also investigate the case of rotating analog ECOs. In this scenario, some of the bound states undergo superradiant amplification and become unstable. In both the rotating and nonrotating case, we calculate numerically transmission/reflection spectra exhibiting the enhanced absorption/amplification. We complement our numerical study with WKB estimates as well as an extension of the Pöschl-Teller toy model which we solve analytically. Our simple model exhibits distinctive properties which could be observed in future analog gravity experiments. We further argue that the observation of the spectral lines could be a way to characterize the effective field theory at play in the vicinity of the vortex core.

We derive the equation of state of a Bose gas with contact interactions using relativistic quantum field theory. The calculation accounts for both thermal and quantum corrections up to one-loop order. We work in the Hartree-Fock-Bogoliubov approximation and follow Yukalov’s prescription of introducing two chemical potentials, one for the condensed phase and another one for the excited phase, to circumvent the well-known Hohenberg-Martin dilemma. As a check on the formalism, we take the nonrelativistic limit and reproduce the known results. Finally, we translate our results to the hydrodynamical, two-fluid model for finite-temperature superfluids. Our results are relevant for the phenomenology of Bose-Einstein condensate and superfluid dark matter candidates, as well as the color-flavor locking phase of quark matter in neutron stars.

We perform a new test of general relativity (GR) with signals from GWTC-2, the LIGO and Virgo catalog of gravitational wave detections. We search for the presence of amplitude birefringence, in which left versus right circularly polarized modes of gravitational waves are exponentially enhanced and suppressed during propagation. Such an effect is present in various beyond-GR theories but is absent in GR. We constrain the amount of amplitude birefringence consistent with the data through an opacity parameter $\kappa$, which we bound to be $\kappa \lesssim 0.74{\mathrm{Gpc}}^{-1}$. Our constraint is derived under an assumption that all GWTC-2 events have a common distance. This result for $\kappa$ is statistically significant, with a Jensen-Shannon divergence of $7\times {10}^{-2}\mathrm{bits}$ compared to an uninformative distribution on $\kappa$. We then use these theory-agnostic results to constrain Chern-Simons gravity, a beyond-GR theory with motivations in quantum gravity. We bound the canonical Chern-Simons lengthscale to be ${\ell }_0\lesssim 1.0\times {10}^3\mathrm{km}$, in agreement with other long-distance measurement results.

We investigate the behavior of classical closed strings in a gravitational wave burst and discover an intriguing resonant behavior where the energy absorbed by the strings is crucially dependent on the amplitude and frequency of the gravitational wave. This behavior can be traced to the well-known behavior of the solutions to the Mathieu equation.

We investigate the structure and stability of the thermal equilibrium states of a spherically symmetric self-gravitating system in a $D$–dimensional asymptotically anti–de Sitter (AdS) spacetime. The system satisfies the Einstein-Vlasov equations with a negative cosmological constant. Due to the confined structure of the AdS potential, we can construct thermal equilibrium states without any artificial wall in the asymptotically AdS spacetime. Accordingly, the AdS radius can be regarded as the typical size of the system. Then the system can be characterized by the gravothermal energy and AdS radius normalized by the total particle number. We investigate the catastrophic instability of the system in a $D$–dimensional spacetime by using the turning point method. As a result, we find that the curve has a double spiral structure for $4\le D\le 10$ while it does not have any spiral structures for $D\ge 11$ as in the asymptotically flat case confined by an adiabatic wall. Irrespective of the existence of the spiral structure, there exist upper and lower bounds for the value of the gravothermal energy. This fact indicates that there is no thermal equilibrium solution outside the allowed region of the gravothermal energy. This property is also similar to the asymptotically flat case.

We study the Joule-Thomson expansion in Einstein-Maxwell theory supplemented with the so-called quasitopological electromagnetism, this in the extended phase space thermodynamic approach. We compute the Joule-Thomson coefficient and depict all relevant inversion and isenthalpic curves in the temperature-pressure plane, determining in this manner the corresponding cooling and heating regions. In contrast with previous related works we show the existence of three branches for the inversion curves which depends on suitable selections of the parameter space of the theory, thus departing from the usual van der Waals behavior which exhibits up to two branches.

Several traversable wormholes (T-WHs) of the Morris-Thorne type have been presented as exact solutions of Einstein-nonlinear electrodynamics gravity, e.g., [A. V. B. Arellano et al., Gen. Relativ. Gravit. 41, 2561 (2009); K. A. Bronnikov, Int. J. Mod. Phys. D 27, 1841005 (2018); K. A. Bronnikov and R. K. Walia, Phys. Rev. D 105, 044039 (2022); P. Cañate and N. Breton, Phys. Rev. D 98, 104012 (2018); P. Cañate et al., Classical Quantum Gravity 37, 055007 (2020); P. Cañate et al., Phys. Rev. D 101, 064010 (2020).]. However, none of these solutions is supported by a nonlinear electrodynamics model satisfying plausible conditions. In this work, we present the first traversable wormhole solution of Einstein-nonlinear electrodynamics gravity coupled to a self-interacting phantom scalar field with a nonlinear electrodynamics model such that in the limit of weak field becomes the Maxwell electrodynamics. Furthermore, we show that this novel T-WH spacetime is also an exact solution of the Einstein-scalar-Gauss-Bonnet theory with a nonlinear electrodynamics source, but now with a real scalar field having a positive kinetic term.

In this work, we construct and study the Carter-Penrose diagram for sonic black hole and white hole analogs as manifested in the analog spacetime embedded inside the flow of hydrodynamic inviscid matter onto astrophysical rotating black holes. For general relativistic black hole accretion in the Kerr metric, we show that linear perturbation of the axially symmetric matter flow having certain geometrical configurations leads to the emergence of black-hole-like acoustic spacetime. Such an analog spacetime is shown to be endowed with one white-hole-like sonic horizon flanked by two black-hole-like acoustic horizons. We construct the compactified causal structures, i.e., the Carter Penrose diagrams for such emergent spacetime to study the corresponding horizon effects. For the first time in literature, the Carter-Penrose formalism is carried out for analog spacetime embedded within a natural large scale fluid flow under the influence of strong gravity.

We develop a thermodynamical model of fermionic dark matter halos at finite temperature. Statistical equilibrium states may be justified by a process of violent collisionless relaxation in the sense of Lynden-Bell or from a collisional relaxation of nongravitational origin if the fermions are self-interacting. The most probable state (maximum entropy state) generically has a “core-halo” structure with a quantum core (fermion ball) surrounded by an isothermal atmosphere. The quantum core is equivalent to a polytrope of index $n=3/2$. The Pauli exclusion principle creates a quantum pressure that prevents gravitational collapse and solves the core-cusp problem of the cold dark matter model. The isothermal atmosphere (which is similar to the Navarro-Frenk-White profile of cold dark matter) accounts for the flat rotation curves of the galaxies at large distances. We numerically solve the equation of hydrostatic equilibrium with the Fermi-Dirac equation of state and determine the density profiles and rotation curves of fermionic dark matter halos. We impose that the surface density of the dark matter halos has the universal value ${\mathrm{\Sigma }}_0={\rho }_0{r}_h=141M_{\odot }/{\mathrm{pc}}^2$ obtained from the observations. For a fermion mass $m=165\mathrm{eV}/c^2$, the “minimum halo” has a mass $(M_h{)}_{\min }={10}^8{M}_{\odot }$ and a radius $(r_h{)}_{\min }=597\mathrm{pc}$ similar to dwarf spheroidals like Fornax. This ultracompact halo corresponds to a completely degenerate fermion ball at $T=0$. This is the ground state of the self-gravitating Fermi gas. For ultracompact dark matter halos with a mass $(M_h{)}_{\min }<M_h<(M_h{)}_{\mathrm{CCP}}=6.73\times {10}^8{M}_{\odot }$ (canonical critical point), the quantum core is surrounded by a tenuous classical isothermal atmosphere. Dark matter halos with a mass $M_h>(M_h{)}_{\mathrm{CCP}}$ are dominated by the classical isothermal atmosphere. They may be purely gaseous (similar to the Burkert profile) or harbor a fermion ball. The gaseous solution is stable in all statistical ensembles. The core-halo solution is canonically unstable (having a negative specific heat) but, for small dark matter halos with a mass $(M_h{)}_{\mathrm{CCP}}<M_h<(M_h{)}_{\mathrm{MCP}}=1.08\times {10}^{10}{M}_{\odot }$ (microcanonical critical point), it is microcanonically stable. By maximizing the entropy at fixed mass and energy we find that the mass of the quantum core scales with the halo mass as $M_c/(M_h{)}_{\min }=1.47[M_h/(M_h{)}_{\min }{]}^{3/8}$. This relation is equivalent to the “velocity dispersion tracing” relation according to which the velocity dispersion in the core $v_c^2\sim G{M}_c/R_c$ is of the same order as the velocity dispersion in the halo $v_h^2\sim G{M}_h/r_h$. We provide therefore a justification of this relation from thermodynamical arguments. The fermion ball represents a large quantum bulge which is either present now or may have, in the past, triggered the collapse of the surrounding gas, leading to a supermassive black hole and a quasar. When $M_h>(M_h{)}_{\mathrm{MCP}}$, the quantum core-halo solution is microcanonically unstable. Large dark matter halos may undergo a gravothermal catastrophe leading ultimately to the formation of a small out-of-equilibrium condensed core or, in the case of very large dark matter halos with $M_h>M_{\mathrm{OV}}$, to a supermassive black hole when the core mass overcomes the Oppenheimer-Volkoff (OV) limit. The isothermal halo is left undisturbed and is in agreement with the Burkert profile. Our model has no free parameter (the mass $m=165\mathrm{eV}/c^2$ of the fermionic particle is determined by the minimum halo) so it is completely predictive. It predicts that the Milky Way should harbor a fermionic dark matter bulge of mass $M_c=9.45\times {10}^9{M}_{\odot }$ and radius $R_c=240\mathrm{pc}$ in possible agreement with the observations. We also consider another model involving a larger fermion mass $m=54.6\mathrm{keV}/c^2$. In this model, a fermion ball of mass $M_c=4.2\times {10}^6{M}_{\odot }$ and radius $R_c=6\times {10}^{-4}\mathrm{pc}$ could mimic the effect of a supermassive black hole at the center of the Milky Way (Sagittarius ${\mathrm{A}}^{*}$). In bigger galaxies, the fermion ball should be replaced by a supermassive black hole of mass $M_{\mathrm{BH}}=2.10\times {10}^8{M}_{\odot }$ which could account for active galactic nuclei. For an even larger fermion mass $m=386\mathrm{keV}/c^2$, a supermassive black hole of mass $M_{\mathrm{BH}}=4.2\times {10}^6{M}_{\odot }$ should be formed in the Milky Way instead of a fermion ball. However, models with a fermion mass $m=54.6\mathrm{keV}/c^2$ predict that ultracompact dark matter halos of mass $\sim {10}^8{M}_{\odot }$ should contain a fermionic core of mass $M_c\sim {10}^4{M}_{\odot }$ and radius $R_c\sim 5\mathrm{mpc}$ similar to intermediate mass black holes, a prediction which may be challenged by observations.

We study the possibility that, after inflation,the inflaton reaches thermal equilibrium with the Standard Model thermal bath and eventually freezes out in the nonrelativistic regime. When the inflaton decay is the sole source of (nonthermal) dark matter, its relic density is automatically suppressed. We delineate parameter space leading to the correct dark matter abundance. The model allows for a significant Higgs-inflaton coupling which may lead to invisible Higgs decay into inflaton pairs at the LHC.

Dark matter annihilation might power the first luminous stars in the Universe. These types of stars, known as dark stars, could form in $({10}^6–10^8)M_{\odot }$ protohalos at redshifts $z\sim 20$, and they could be much more luminous and larger in size than ordinary stars powered by nuclear fusion. We investigate the formation of dark stars in the self-interacting dark matter (SIDM) scenario. We present a concrete particle physics model of SIDM that can simultaneously give rise to the observed dark matter density, satisfy constraints from astrophysical and terrestrial searches, and address the various small-scale problems of collisionless dark matter via the self-interactions. In this model, the power from dark matter annihilation is deposited in the baryonic gas in environments where dark stars could form. We further study the evolution of SIDM density profiles in the protohalos at $z\sim 20$. As the baryon cloud collapses due to the various cooling processes, the deepening gravitational potential can speed up gravothermal evolution of the SIDM halo, yielding sufficiently high dark matter densities for dark stars to form. We find that SIDM-powered dark stars can have similar properties, such as their luminosity and size, as dark stars predicted in collisionless dark matter models.

Ultralight axionlike particles (ALPs) are compelling dark matter candidates because of their potential to resolve small-scale discrepancies between $\mathrm{\Lambda }\mathrm{CDM}$ predictions and cosmological observations. Axion-photon coupling induces a polarization rotation in linearly polarized photons traveling through an ALP field; thus, as the local ALP dark matter field oscillates in time, distant static polarized sources will appear to oscillate with a frequency proportional to the ALP mass. We use observations of the cosmic microwave background from SPT-3G, the current receiver on the South Pole Telescope, to set upper limits on the value of the axion-photon coupling constant $g_{\varphi \gamma }$ over the approximate mass range ${10}^{-22}–{10}^{-19}\mathrm{eV}$, corresponding to oscillation periods from 12 hours to 100 days. For periods between 1 and 100 days ($4.7\times {10}^{-22}\mathrm{eV}\le m_{\varphi }\le 4.7\times {10}^{-20}\mathrm{eV}$), where the limit is approximately constant, we set a median 95% C.L. upper limit on the amplitude of on-sky polarization rotation of 0.071 deg. Assuming that dark matter comprises a single ALP species with a local dark matter density of $0.3\mathrm{GeV}/{\mathrm{cm}}^3$, this corresponds to $g_{\varphi \gamma }<1.18\times {10}^{-12}{\mathrm{GeV}}^{-1}\times (\frac{m_{\varphi }}{1.0\times {10}^{-21}\mathrm{eV}})$. These new limits represent an improvement over the previous strongest limits set using the same effect by a factor of $\sim 3.8$.

We derive a modified Balitskii-Fadin-Kuraev-Lipatov equation with the rapidity veto that originates from external kinematic constraint. Though it is a formally subleading power contribution, such kinematic effect becomes very important in the threshold region, where there is no sufficient phase space for the small $x$ evolution to be fully developed. We also investigate the phenomenological consequences of the kinematic constraint Balitskii-Fadin-Kuraev-Lipatov equation in the forward particle production processes in pp and eA collisions. It is shown that particle yield at large transverse momentum is significantly suppressed in the threshold region.

The $W$ boson mass is one of the most important electroweak precision observables for testing the Standard Model (SM) or its extensions. The very recent measured $W$ boson mass at the Collider Detector at Fermilab (CDF) shows about $7\sigma$ deviations from the SM prediction, which may challenge the internal consistency of the SM. By performing the global electroweak fit with the new $W$ boson, we present the new values of the oblique parameters: $S=0.06\pm 0.10$, $T=0.11\pm 0.12$, $U=0.13\pm 0.09$, or $S=0.14\pm 0.08$, $T=0.26\pm 0.06$ with $U=0$ and the corresponding correlation matrices, which strongly indicates the need for the nondegenerate multiplets beyond the SM. As a proof-of-concept, we show that the new results can be accommodated in the two-Higgs doublet model, where the charged Higgs boson has to be either heavier or lighter than both two heavy neutral Higgs bosons. The collider search for these non-SM Higgs bosons will provide a complementary way to test the new physics for $W$ boson mass anomaly.

Pulsar timing arrays (PTAs) are exceptionally sensitive detectors in the frequency band $\mathrm{nHz}\lesssim f\lesssim \mu \mathrm{Hz}$. Ultralight dark matter (ULDM), with mass in the range ${10}^{-23}\mathrm{eV}\lesssim m_{\varphi }\lesssim {10}^{-20}\mathrm{eV}$, is one class of DM models known to generate signals in this frequency window. While purely gravitational signatures of ULDM have been studied previously, in this work we consider two signals in PTAs which arise in the presence of direct couplings between ULDM and ordinary matter. These couplings induce variations in fundamental constants, i.e., particle masses and couplings. These variations can alter the moment of inertia of pulsars, inducing pulsar spin fluctuations via conservation of angular momentum, or induce apparent timing residuals due to reference clock shifts. By using mock data mimicking current PTA datasets, we show that PTA experiments outperform torsion balance and atomic clock constraints for ULDM coupled to electrons, muons, or gluons. In the case of coupling to quarks or photons, we find that PTAs and atomic clocks set similar constraints. Additionally, we discuss how future PTAs can further improve these constraints, and detail the unique properties of these signals relative to the previously studied effects of ULDM on PTAs.