142 research outputs found
Surprises from complete vector portal theories: New insights into the dark sector and its interplay with Higgs physics
No full textRecommended from our members
On the Common Origin of Dark and Baryonic Matter Abundances and Cosmological Probes of the Dirac Neutrino
No full textAlthough the Standard Model has been a successful description of observedparticles and interactions, there exist open questions and observations which
motivate physics beyond its framework. Of particular importance are the need
for new particles and interactions to explain the origins of the observed baryon
asymmetry, the nature of dark matter, and generation of neutrino mass. This
work is motivated by the coincidental similarity between the baryon asymmetry
and abundance of dark matter which, when taken together with their mysterious
origins, constitutes a cosmological triple puzzle. In this thesis, unique mecha-
nisms which propose new interactions and symmetries between quarks and dark
matter candidates are used to unambiguously address this triple puzzle. These
models predict interesting experimental signatures such as induced proton de-
cay. Additionally, new frameworks which generate neutrino masses such as
gauged and Dirac leptogenesis, utilize new interactions for neutrinos
which would lead to additional, measurable contributions to and
Motivated by these imprints, this thesis also includes a new mechanism to test
the Dirac nature of the neutrino by correlating variables used by cosmological
and terrestrial probes
Recommended from our members
Phenomenology of Axion Fields and Topological Defects
No full textIn the conventional misalignment mechanism, the axion field is assumed to start with zero initial velocity. However, we introduce an alternative scenario in which the axion field possesses a nonzero initial velocity, potentially due to the breaking of the Peccei–Quinn (PQ) symmetry during the early Universe. Depending on the initial velocity and the sequence of events between PQ symmetry breaking and inflation, this novel scenario can amplify or diminish the expected axion relic abundance compared to the conventional prediction. Consequently, this opens up new parameter regions for axion dark matter models.Global cosmic strings, anticipated in various non-standard models, generate primordial gravitational waves detectable by instruments. We refine the analytical Velocity-dependent One-Scale (VOS) model through recent simulation outcomes, revealing the gravitational wave spectrum produced by global string networks, including Goldstone emission. Our findings present a technique to detect signals from the early universe before Big Bang nucleosynthesis, impacted by the non-standard pre-BBN equation of state and new relativistic particles.Early dark energy, relieving the Hubble tension, imprints discernible characteristics on the primordial stochastic gravitational wave background originating from cosmic string networks. This signal stands out in planned gravitational wave experiments, distinctly separate from other cosmological and astrophysical signals in the gravitational wave frequency spectrum.In the context of axion-like particle (ALP) dark matter theories, we explore enhanced early galaxy formation through the kinetic misalignment mechanism. This has potential relevance to the excess observed by the James Webb Space Telescope (JWST) while adhering to constraints. Viable parameter space is identified for ALP mass within the range of $10^{-22}{\rm eV}Through advanced simulations and analytical modeling, we conduct an updated analysis of long-lived axion domain wall (DW) networks. By scrutinizing energy loss mechanisms and calculating axion emissions from the DW network, we determine their contribution to axion dark matter density. While our results are consistent with prior research, disparities arise, particularly in predicting DM abundance. These disparities could profoundly impact axion phenomenology on a larger scale
Warped Dipole Completed, with a Tower of Higgs Bosons
No full textIn the context of warped extra-dimensional models which address both the Planck-weak- and flavor-hierarchies of the Standard Model (SM), it has been argued that certain observables can be calculated within the 5D effective field theory only with the Higgs field propagating in the bulk of the extra dimension, just like other SM fields. The related studies also suggested an interesting form of decoupling of the heavy Kaluza-Klein (KK) fermion states in the warped 5D SM in the limit where the profile of the SM Higgs approaches the IR brane. We demonstrate that a similar phenomenon occurs when we include the mandatory KK excitations of the SM Higgs in loop diagrams giving dipole operators for SM fermions, where the earlier work only considered the SM Higgs (zero mode). In particular, in the limit of a quasi IR-localized SM Higgs, the effect from summing over KK Higgs modes is unsuppressed (yet finite), in contrast to the naive expectation that KK Higgs modes decouple as their masses become large. In this case, a wide range of KK Higgs modes have quasi-degenerate masses and enhanced couplings to fermions relative to those of the SM Higgs, which contribute to the above remarkable result. In addition, we find that the total contribution from KK Higgs modes in general can be comparable to that from the SM Higgs alone. It is also interesting that KK Higgs couplings to KK fermions of the same chirality as the corresponding SM modes have an unsuppressed overall contribution, in contrast to the result from the earlier studies involving the SM Higgs. Our studies suggest that KK Higgs bosons are generally an indispensable part of the warped 5D SM, and their phenomenology such as signals at the LHC are worth further investigation.In the context of warped extra-dimensional models which address both the Planck-weak- and flavor-hierarchies of the Standard Model (SM), it has been argued that certain observables can be calculated within the 5D effective field theory only with the Higgs field propagating in the bulk of the extra dimension, just like other SM fields. The related studies also suggested an interesting form of decoupling of the heavy Kaluza-Klein (KK) fermion states in the warped 5D SM in the limit where the profile of the SM Higgs approaches the IR brane. We demonstrate that a similar phenomenon occurs when we include the mandatory KK excitations of the SM Higgs in loop diagrams giving dipole operators for SM fermions, where the earlier work only considered the SM Higgs (zero mode). In particular, in the limit of a quasi IR-localized SM Higgs, the effect from summing over KK Higgs modes is unsuppressed (yet finite), in contrast to the naive expectation that KK Higgs modes decouple as their masses become large. In this case, a wide range of KK Higgs modes have quasi-degenerate masses and enhanced couplings to fermions relative to those of the SM Higgs, which contribute to the above remarkable result. In addition, we find that the total contribution from KK Higgs modes in general can be comparable to that from the SM Higgs alone. It is also interesting that KK Higgs couplings to KK fermions of the same chirality as the corresponding SM modes have an unsuppressed overall contribution, in contrast to the result from the earlier studies involving the SM Higgs. Our studies suggest that KK Higgs bosons are generally an indispensable part of the warped 5D SM, and their phenomenology such as signals at the LHC are worth further investigation.In the context of warped extra-dimensional models which address both the Planck-weak- and flavor-hierarchies of the Standard Model (SM), it has been argued that certain observables can be calculated within the 5D effective field theory only with the Higgs field propagating in the bulk of the extra dimension, just like other SM fields. The related studies also suggested an interesting form of decoupling of the heavy Kaluza-Klein (KK) fermion states in the warped 5D SM in the limit where the profile of the SM Higgs approaches the IR brane. We demonstrate that a similar phenomenon occurs when we include the mandatory KK excitations of the SM Higgs in loop diagrams giving dipole operators for SM fermions, where the earlier work only considered the SM Higgs (zero mode). In particular, in the limit of a quasi IR-localized SM Higgs, the effect from summing over KK Higgs modes is unsuppressed (yet finite), in contrast to the naive expectation that KK Higgs modes decouple as their masses become large. In this case, a wide range of KK Higgs modes have quasi-degenerate masses and enhanced couplings to fermions relative to those of the SM Higgs, which contribute to the above remarkable result. In addition, we find that the total contribution from KK Higgs modes in general can be comparable to that from the SM Higgs alone. It is also interesting that KK Higgs couplings to KK fermions of the same chirality as the corresponding SM modes have an unsuppressed overall contribution, in contrast to the result from the earlier studies involving the SM Higgs. Our studies suggest that KK Higgs bosons are generally an indispensable part of the warped 5D SM, and their phenomenology such as signals at the LHC are worth further investigation
Phenomenology of Hidden Sector Physics.
No full textThe existence of a hidden sector, composed of Standard Model (SM) singlets and the interactions between them, is well-motivated by many beyond-the-SM theories, such as GUT theories, string-inspired models and supersymmetry-breaking models. In addition to sharing weak gravity-induced interactions with the visible sector, such SM singlets can couple to the SM Lelds in various other ways. One well motivated hidden sector scenario is that associated with a beyond-the-SM gauge symmetry which is broken via the Higgs mechanism. Although the collider phenomenology of
such models is rich and well-documented, few obvious cosmological signatures for them are known. The physics of cosmic strings provides a promising cosmological probe of such hidden sectors, applicable for a general class of symmetry breaking patterns in the hidden sector. This thesis discusses the phenomenology of hidden sectors, including LHC signatures of a hidden sector Higgs boson, the physics of
cosmic strings from supersymmetric flat-directions, and dark matter production from a general cosmic string network. We conclude that there are viable prospects for seeing signals of a hidden sector both at the LHC and in cosmological observations.PhDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60760/1/yocui_1.pd
Exploring the politics of <i>luzibo kusangana</i>:The potential of Tonga local, integrated and hybrid knowledge for equitable landscape approaches in Southern Zambia
No full textLandscape approaches – a negotiated form of landscape governance mobilising landscape actors to discuss and reach consensus on trade-offs between competing land uses and development-conservation goals – involve interactions between different knowledge systems. Based on a case study in Southern Zambia, this thesis examines what role local knowledge plays in the conservation and sustainable management of natural resources, how it evolves in the interactions with practitioner and scientific knowledge, how knowledge integration for conservation and natural resource management is shaped in practice and say local knowledge holders have in knowledge interactions and decision-making in multistakeholder platforms. Collectively, these insights answer the question: How do local knowledge and practices and their integration and hybridisation with other knowledge systems contribute to the implementation of integrated landscape approaches for conservation and natural resource management in Kalomo District, Zambia? The author combines systematic literature reviews with the analysis of empirical data collected through an innovative combination of photovoice and walking interviews. Based on the findings, the author advocates more equitable knowledge sharing and co-production in landscape approaches and multistakeholder platforms, based on greater authority and validation of Indigenous and local knowledge in landscape approaches, a decolonial perspective, and attention to the rights of Indigenous Peoples and local communities
New Perspectives on Axion Misalignment Mechanism
No full textA zero initial velocity of the axion field is assumed in the conventional
misalignment mechanism. We propose an alternative scenario where the initial
velocity is nonzero, which may arise from an explicit breaking of the PQ
symmetry in the early Universe. We demonstrate that, depending on the specifics
about the initial velocity and the time order of the PQ symmetry breaking vs.
inflation, this new scenario can alter the conventional prediction for the
axion relic abundance in different, potentially significant ways. As a result,
new viable parameter regions for axion dark matter may open up.Comment: 7 pages, 7 figures; UPDATE to a published versio
Probing Leptogenesis with the Cosmological Collider
No full textLeptogenesis is generally challenging to directly test due to the very high
energy scales involved. In this work we propose a new probe for leptogenesis
with cosmological collider physics. With the example of a cosmological Higgs
collider, we demonstrate that during inflation leptogenesis models can produce
detectable primordial non-Gaussianity with distinctive oscillatory patterns
that encode information about the lepton-number violating couplings, the
Majorana right-hand neutrino masses, and the CP phases, which are essential to
leptogenesis.Comment: Journal version, 6 pages + 3 pages of supplemental materia
Exploring the politics of <i>luzibo kusangana</i>:The potential of Tonga local, integrated and hybrid knowledge for equitable landscape approaches in Southern Zambia
No full textLandscape approaches – a negotiated form of landscape governance mobilising landscape actors to discuss and reach consensus on trade-offs between competing land uses and development-conservation goals – involve interactions between different knowledge systems. Based on a case study in Southern Zambia, this thesis examines what role local knowledge plays in the conservation and sustainable management of natural resources, how it evolves in the interactions with practitioner and scientific knowledge, how knowledge integration for conservation and natural resource management is shaped in practice and say local knowledge holders have in knowledge interactions and decision-making in multistakeholder platforms. Collectively, these insights answer the question: How do local knowledge and practices and their integration and hybridisation with other knowledge systems contribute to the implementation of integrated landscape approaches for conservation and natural resource management in Kalomo District, Zambia? The author combines systematic literature reviews with the analysis of empirical data collected through an innovative combination of photovoice and walking interviews. Based on the findings, the author advocates more equitable knowledge sharing and co-production in landscape approaches and multistakeholder platforms, based on greater authority and validation of Indigenous and local knowledge in landscape approaches, a decolonial perspective, and attention to the rights of Indigenous Peoples and local communities
Exploring the politics of <i>luzibo kusangana</i>:The potential of Tonga local, integrated and hybrid knowledge for equitable landscape approaches in Southern Zambia
No full textLandscape approaches – a negotiated form of landscape governance mobilising landscape actors to discuss and reach consensus on trade-offs between competing land uses and development-conservation goals – involve interactions between different knowledge systems. Based on a case study in Southern Zambia, this thesis examines what role local knowledge plays in the conservation and sustainable management of natural resources, how it evolves in the interactions with practitioner and scientific knowledge, how knowledge integration for conservation and natural resource management is shaped in practice and say local knowledge holders have in knowledge interactions and decision-making in multistakeholder platforms. Collectively, these insights answer the question: How do local knowledge and practices and their integration and hybridisation with other knowledge systems contribute to the implementation of integrated landscape approaches for conservation and natural resource management in Kalomo District, Zambia? The author combines systematic literature reviews with the analysis of empirical data collected through an innovative combination of photovoice and walking interviews. Based on the findings, the author advocates more equitable knowledge sharing and co-production in landscape approaches and multistakeholder platforms, based on greater authority and validation of Indigenous and local knowledge in landscape approaches, a decolonial perspective, and attention to the rights of Indigenous Peoples and local communities
- …
